Three points, for what it's worth:
1. The company offering the FAA examinations at Staverton has closed. I did mine there a couple of years ago, and a fine facility it was.
2. I understand that the latest FAA rules do not permit adding an FAA IR to a "reciprocal" licence. That may not be correct, but I've been told it from several directions. If so, it's a full FAA PPL first.
3. I've been told (by also impeccable sources) that you can't take an FAA checkride in the UK at the moment. It has to be in the USA. There are several folks saying that you *can* still do the checkride in the UK, but nobody can point to anyone who's done one here in the past six months.
I've heard only good things about Tom Hughston at Norwich for the writtens.
If Naples Air Center were still doing flight training, I'm sure they'd be able to give chapter and verse.