The Ultima Forever team has released a map of the Town of Britain on their Facebook page.
You can view it in all its 1650 x 1311 glory on the Ultima Forever: Map of Britain page.
Update: Jeff Skalski posted this in response to comments on the main Ultima Codex
All hand painted. No 3D assets used as guides. The art team did an amazing job. This was one town we pretty much rebuilt from scratch just because we knew it would be a hub for a lot of player activity. The other towns follow more closely the classic towns as we all remember.