The last I heard, some time ago, was that no individual or organisation based in the UK would be allowed to have a .eu domain after Brexit. Some workarounds were postulated but didn't seem practicable. So I bagged mellish.uk when the chap who handles my domain registration told me it was available, but then waited until we found out whether Brexit would be happening before starting to tell people.

(Probably) losing my .eu domain will be one of the lesser consequences of Brexit, but we don't need to discuss that here.