Start off by having a search on here and by reading the stickies, some of them cover this particular question and there are plenty of general faa licencing threads, also get a copy of cap804 from the uk caa website. That will get you started on dealing with the complexities but the short answer is that whilst the training in the usa is countable in theory for the uk/easa in practice you are going to be doing the uk stuff nearly from scratch if you want a uk licence, or you can fly day vfr on your faa ppl although that privilege sounds like its days are numbered