The validation/cornflakes box FAA ppl that you will receive will be based on your foreign license. you need to keep your EASA license and certificate current in every respect in order to exercise the FAA PPL you will receive based on your foreign license.
if you’re planning on flying an N reg in the UK to avoid all the currency and beuracracy requirements that is EASA then you’re best to bite the bullet and spend a week and about 3-5k getting your FAA PPL or CPL and class 1 or 2 medical and be done with it and give EASA the middle finger.