One minor complication is that the US private licence requires night cross countries of 100 mi or so, something that would be difficult to do in UK when virtually every airfield is closed. I suspect this might affect the night aspect of a based on licence even with a night rating.
I did check up on this and was advised that if you have night priviledges on the foreign licence, you do not need to meet the night training requirements for the FAA private certificate. If you were getting a full FAA private certificate based on flying experience, then you would have to have done the 100 mile night cross country.