That is a really good question. The truth is that evidence for any sort of "cultural continuity" is scant.
One word of caution though. I generally hesitate to use the word "ritual" in an archaeological context. Too often, the word has been used as a synonym for "I don't know", or, as Paul Bahn put it:
Ritual - All-purpose explanation used where nothing else comes to mind
Bahn, 1989, p62
No, there's no evidence for cultural continuity from the Neolithic to the Iron Age. However, as you might expect, we do see some evidence of elements of continuity from the late Neolithic into the Bronze age, and also from the late Bronze Age into the Iron Age.
The Neolithic period in Britain coincides with the introduction of farming and pottery, and dates from about 4000 BC to about 2,500 BC. The main monuments associated with the Neolithic period in Britain are:
- Chambered tombs
- Causewayed enclosures
- Stone circles
Although a few burials of Neolithic individuals have been found, some form of communal burial seems to have been the norm in the Neolithic period. Large communal chambered tombs were generally placed close to settled areas and normally sited in dominant positions. A good example of this is the West Kennet long-barrow in Wiltshire, which really does dominate the skyline. Building these tombs clearly took a lot of effort. So building one of these tombs sent a very clear message: "We are here, and we intend to remain here."
There are suggestions that funerary practices at this date included excarnation, after which surviving remains were gathered and placed in the communal tombs. It is possible that these remains were brought out on special occasions, perhaps in the course of some ancestor-worship rites.
West Kennet long barrow was finally sealed around 2200 BC. The main passage was filled with earth, and a large stone was placed across the entrance. It had been in use for something between 1000 and 1500 years! We do not know why these communal burials went out of fashion, but evidence for later burial rites seems to be about the individual, rather than the community.
Causewayed enclosures were monuments of the early Neolithic. Normally (although not exclusively) sited on the tops of hills, these sites consist of an area enclosed by banks and ditches. They do not appear to be defensive sites, since the banks have wide causeways between them (which give the monuments their name).
There are more than 70 of these sites in Britain (and even more on the continent). We really don't know what function they served (yes, many older archaeological texts do describe them as having a "ritual function"). They don't appear to have been occupation sites, and no evidence of permanent structures have been found inside.
A henge monument is an area enclosed by an earth bank with an internal ditch. Most date to the late Neolithic, and so may take on the (unknown) function(s) previously provided by causewayed enclosures. Many henge monuments, but by no means all, also have a stone circle. Stonehenge does have a bank and ditch, but it not actually a true henge, since the ditch runs outside the bank. In any event, the bank and ditch are often overlooked when people focus on the stone circles!
Avebury is another henge enclosure which also has an associated stone circle. Because of its size, Avebury is sometimes referred to as a "Super-henge". Other "Super-henges" include Marden henge, Durrington Walls and Mount Pleasant Henge).
And, once again, we don't actually know what they were for! The henges clearly enclose an important, perhaps "sacred", space (I'm trying to avoid the word "ritual" here, but you'll find it sprinkled liberally in the textbooks!).
Stone circles are, unsurprisingly, large stones arranged in circles. Except they're not always circular (many are actually ovals), and not all were constructed from stone (e.g. the timber circles at Woodhenge and Seahenge).
This class of monument was in use for a very long time. The earliest stone circles date to the early Neolithic (say about 3300 BC), and the latest date to the later Bronze Age (about 900 BC). The function of these monuments has long been debated, and those debates will undoubtedly continue for many years to come. Many stone circles show some astronomical alignments, and this may relate to their function (or, perhaps, one part of their function). The truth is that, once again, we just don't know.
The Bronze Age in Britain dates from about 2500 BC to about 800 BC. Burials in barrows with a burial mound are, perhaps, the defining feature of Bronze Age funerary practice in Britain. It seems the change in burial practice accompanied the introduction of bronze-metalworking technology (perhaps literally in the case of the Amesbury Archer).
One major problem problem is that there just aren't enough barrows to account for the whole population. If "high-status" individuals were buried in barrows, what happened to everybody else? Perhaps excarnation continued to be practised (this might be a possible function for those henge sites). We know that there was "ritual" (yes, there's that word again) deposition of metalwork in water at Bronze Age sites like Flag Fen. It is possible that remains were gathered after excarnation and also deposited in rivers.
We also have increasing evidence of cremation, particularly in the later Bronze Age, with the remains buried in pits (often around existing barrows). Perhaps the remaining population were also cremated and their ashes then scattered. The truth is that we really just don't know what happened to the bulk of the population of Bronze Age Britain when they died.
As mentioned above, stone circles continued to be erected into the Bronze Age. At other sites, like Stonehenge, the arrangement of the stone circle changed over time. This has been extensively studied. We have a very clear idea about what happened, and when, but we can only guess when it comes to the question of why?
One unique monument from the early Bronze Age in Britain is Silbury Hill. This is the largest man-made mound in Europe. We have no idea of its function, but a series of excavations appear to show that there was never a burial beneath it.
Personally, I suspect that Silbury Hill may provide an insight into the question of why other large-scale prehistoric monuments were built.
At the beginning of the Bronze Age most of the population was involved in some form of agricultural work for most of the year. However, at certain times of the agricultural year there is less to do than there is at others. We can infer from residue analysis that they had alcoholic beverages. It seems reasonable to conclude that, then as now, the combination of young people with time on their hands and easy access to alcohol is likely to lead to social problems.
At the same time, there is the natural desire (which we have already seen with the Neolithic long barrows) to place a mark on the landscape. Something that says: "This is our place. And we are here for the long term".
Given these drivers, it is possible to see many of the early large-scale monuments as communal projects, intended to set their stamp on the landscape, while also ensuring that idle hands were occupied.
Some "authority", whether that was an individual "leader", or a group of "elders", or a group of wives desperate to get their husbands out of the way, or something else entirely, decided that they should build Long-barrows; causewayed-enclosures; henges; stone circles ...
Silbury Hill may just have been the largest of these projects where, perhaps, the journey was just as important as the destination.
Although that interpretation is consistent with the evidence, it remains just one possible interpretation. However, it is one that I find persuasive.
It is generally accepted that the Iron Age in Britain begins around 800 BC. By this point all the earlier large-scale monuments appear to have gone out of use.
This is a period characterised by large-scale defensive architecture. Hill-forts appear for the first time across much of Britain, along with defensive brochs in Scotland. Some of the best-known (and most spectacular) hill-forts are Maiden Castle in Dorset, Cadbury Castle in Somerset and Danebury Hill in Hampshire.
These sites do suggest a more "warlike" culture in the Iron Age (although it has been suggested that it merely indicates a greater accumulation of wealth and a higher standard of living). There does not seem to be a correlation between hill-forts and earlier large-scale sites.
Many hill-forts did contain structures (unlike the earlier causewayed enclosures), although it is unclear whether they were permanently occupied, or whether they were only used this way intermittently.
What is clear is that the concept of a central "authority" who could order the construction of large-scale monuments was still around in the Iron Age. By the later Iron Age, when we begin to have contact with Rome, this central authority seems to have been and individual "king". Whether that was also the case at the beginning of the Iron Age, 700 years earlier, is unclear.
It also seems clear that the motivation for building these large-scale structures was very different in the Iron Age from the motivation that had driven the construction of large-scale structures in earlier periods. Iron Age hill-forts and brochs seem to be fundamentally about security.
Burial practices at the beginning of the Iron Age show a continuation of the tradition of cremation from the later Bronze Age. Later, we see a return to individual, inhumation burials for "high status", or "elite", individuals, and this practice continues up to the Roman period.
The so-called bog bodies, like Lindow Man (a.k.a. "Pete Marsh") might suggest that there was a continuation of the practice of "ritual" (there it is again!) deposition in water from the Bronze Age into the Iron Age.
So, to answer your question, no there wasn't a continuation of practice from the Neolithic to the Iron Age.
The Iron Age peoples seem to have abandoned the earlier sites that their Neolithic and Bronze Age ancestors had created. In fact, although we can detect some "cultural continuity" from the Neolithic to the Bronze Age, the Iron Age seems to show a clear break with the large-scale "ritual" sites of earlier periods.
We do see some continuity in burial practices from the later Bronze Age into the early Iron Age, but that is to be expected. There is no evidence for a great influx of people who might have brought new practices and traditions with them. The people of the early Iron Age were the grandchildren and great-grandchildren of the people of the later Bronze Age. Changes to things like burial practices would have been gradual (I suspect that the monuments of the Bronze Age were also abandoned gradually, but that is not preserved in the archaeological record).
We don't know what forces drove the people of the Iron Age to build defensive structures like hill-forts and brochs. It is a natural instinct to want to protect what you have. It seems likely that there was a perceived threat and that these new monumental structures were the response, but there doesn't seem to be any evidence that they were built on the sites of earlier structures, "ritual" or otherwise.