The kindly Deputy Head of Collections at Manchester Museum took a look at my stone and gave the following response.
Your 'bead' is almost certainly a fossil called porosphaera globularis. There has been some discussion as to whether they were used as beads in prehistoric times, several hundred thousand years ago. Fossils re-used in this way often have rounded perforations where the cord on which they were suspended abraded the stone matrix. Sometimes it is possible to see wear marks and depressions caused by the adjacent beads on the cord rubbing against each other. However, as far as I can see such re-use is mainly found in southeast Britain and on the Continent, probably because at the time northern Britain was simply too cold because of the impact of the Ice Ages.
I suspect your example is a fossil because the perforations are rough and not rounded as you might expect is a cord had abraded the stone. There isn't any sign of cupping or depressions where any other beads might have rubbed against this bead if it had been suspended on a cord. Your example too, being found in the northwest is outside the region where re-used fossil beads have been found. For these reasons, I am confident that your example is, therefore, a fossil and has not been used in the past by early human beings such as Homo heidelbergensis.
I'm pretty sure that if asked I may say it was used as jewellery though...whoever let the truth get in the way of a good story!
Thanks for your help all.