Despite the fact that it never ended up happening, a Nazi invasion of England was kind of a common sense inevitability for a while during the beginning of World War 2. Had the Battle of Britain gone the other way, (or whatever alternate history conditions you prefer), a Nazi invasion across the channel was a real possibility.
Surely Britain had plans for what they would do, in that case? I can only imagine that they had numerous scenarios, depending on how the invasion went down. How did these plans match up to the German preparations? How much detail do we know about how the defense of Britain would have gone? What tactics did they plan on using, where did they anticipate the main battles to occur? Did the British commanders think they could successfully repulse a Nazi invasion of England, or were the plans geared more toward slowing them down and making it "not worth their while"?