Fallout London (FOLON), a Fallout 4 mod, is so popular that it already has over 220 mods (sub-mods). That's truly an epic success, which means fans are happy to experience an apocalypse in the UK setting. While not all mods are great, you can find some real mod gems.
How to play Fallout: London!
Two weeks after its launch, Fallout London received a lot of praise from fans, especially English ones. While they all agree that this mod is much better than expected, there is still work to be done. Luckily, the modding community has jumped in and created mods that help with optimization, in-game detail changes, item fixes, etc. Just like Fallout 4 mods, modders try to improve the game and make it more English, and therefore more immersive.
The most popular mod is Downgrader, which lets you go back to the next-gen version of Fallout 4. This FOLON mod is essential if you plan on making your own. Aside from technical mods that make your gameplay more accessible, I enjoyed the world-building mods the most. One of them is the Britpick Consistency Patch, which replaces American elements (e.g. a cricket bat instead of a baseball bat).
For similar purposes, you can also try the Workshop Rearranged Patch, which alters items to match the London environment. For example, things will appear from the Commonwealth, such as a caravan hitching post that requires you to perform a favor in Bunker Hill, USA.