I did once consider making something for the UK and it would have consisted of the first map area Seppel shows.
Why you might ask? Well as someone who lives in North West England the map would allow for a number of things, first of all you would get all the normal stuff of legend in the southern part of the UK but remember the main cities in the North West where I live were also the subject of Luftwaffe attacks, namely Manchester and Liverpool, an old friend of mine is a decedent of a Polish Hurricane pilot who ended up flying Hurricanes from Squires Gate airfield in Blackpool. Besides this there is much of historical aviation importance, Warton airfield was used to train American bomber crews, and is still the home of Bae and the Tytphoon, seaplanes came to be in the Lake District and Northern Ireland so a lot of historical airfields both civil and military to research and plan missions for.
Let us not forget the Irish Republic, like Switzerland their pilots spent much of the war intercepting stray German aircraft that got lost over England and ventured their way so a few stories to tell there and the chance to do some Irish skins for Gladiator and Hurricane amongst others.
The sea all around the coast was of great importance to the UK with convoys heading across the Atlantic ending up in Liverpool and other ports and the need to constantly guard convoys and search for German submarines was a daily task for Coastal Command.
Lots of interest so why did I not do it? Well because I live here in Preston, I am very close to all the main areas mentioned for the North West and used to frequent Squires Gate many times both as a drinker and flyer, never at the same time I might add and it was my feeling I would get stuck just building local landscapes and buildings well known to me and so would most likely never have got it finished!
Blackpool Tower, local football stadiums, ports and railway hubs, airfield architecture, you get the gist I think, some of those just within 17 miles of me would have become a main focus and the remainder of the map would probably have remained unpopulated.
Maybe one day I might dig out those mapping tools again.
Take care and be safe.
Wishing you all the very best, Pete.