>>36907786being a bong I might like a region based on the UK but the bad thing is that it would be based on meme things like beefeaters and cockneys.
I'm from a part called the west midlands and I could imagine a fanciful version of that area. I remember walking up and down the canals with my friends so that might be a fun way to lay out a region. It would be land-locked with a network of canals as the way of getting around. There's a history of industrialization, so there could be abandoned victorian factories/structures as dungeons (I had a thought of a regional variation of a rusty Klinklang that's steel/poison). There could also be old mines that could be dungeons as well.
The legendaries/mythical pokemon could have an Arthurian theme to them. I'm not sure exactly what that would mean off the top of my head.