This is a map I've been working on for a while, including the Isle of Great Britain (England, Scotland, Wales) and Ireland.
Start plots and resources are randomised. Jungle represents marsh/wetland, whilst tundra is moorland, etc.
It is 64x102 tiles. Uncompressed size
Great Britain is mainly accurate south of the Great Glen, although northern Scotland is a little squished in order to allow navigation , and I'm not sure how well Ireland came out - if anyone has suggestions on how to improve it, I'd be happy to update the resource.
Right now this is playable as a standalone, although I am in the process of planning a mod around it.
Spoiler Map of Britannia :
Britannia Map 2018-12-14
Huge Map of the British Isles and Northern Francia