The United Kingdom is a great place to cycle in general as there's plenty of small country roads and interesting new small towns to discover, perhaps much like the rest of Europe, as opposed to the United States, which likely has some huge infinitely long straight roads with a lot of nothing in between.
Of particular interest is the large amount of airfields and small air raid shelters in the fields, an ominous reminder of world war 2. The airfields are in various states, from functional military fields, many converted to civilian usage, some have barely any tarmac left but still see usage. And some were just completely abandoned and decayed and became recreation grounds and farms. The UK is therefore also a great place to be if you want to learn to fly as a hobby!
Good starting point:
Next, you want to decide about nice destinations to reach/go through, and these are good ideas to look into:
- Area of Outstanding Natural Beauty
- National Trust
- Royal Society for the Protection of Birds (RSPB)