For some reason typing in "ethnic map of Britain" into Google image search doesn't produce an ethnic map of Britain. At least not in the top 100 or so. This is strange since you can Google an ethnic map of somewhere far away, like Afghanistan.
There is one hit, an Independent newspaper headline, for "race map of Britain". That's from 2006 and there are interesting details in the captions, so I'll post it again below. As you can see, the title is a misnomer as 99.9% of the "diversity" is in England.
This map is not quite what I was looking for because a "diversity" map includes Jewish people and no doubt Poles, Irish and other white foreigners. I'd like to know at least the proportion of white to non-white. That map would better show up broad cultural and linguistic differences between Britons.
So the only thing to do was to draw up a map myself. Wikipedia is not the most up to date or accurate source on demographics but it was the quickest and good enough for starters. Here it is that map.
(This is not yet an ethnic map but it's a start.)
Again, like the Independent map diversity is very much an English phenomenon. The regions, counties with long coastlines, hills, the large land areas with low population densities have the lowest concentration of non-white Britons.
Our largest non-white groups, South Asian and Black Britons, are mostly to be found on the flat lands of England, along a SE/NW economic corridor between London and Manchester. The corridor also extends down to East Sussex which may have something to do with the Channel Tunnel and ferry ports, or it could just be because those counties are close to London.
It's pretty startling how the South West, Scotland, Wales and Northern Ireland have got away with so little diversity, all +98% white. I wonder if there is a reason for that?