No worries. The best thing you can do is to study for the oral, really. I considered exactly the same route as you and I decided it was too much like hard work in the uk, plus the cost at farnborough and getting an entry signoff and timings etc. I had a slight advantage in that I had already taken the written once a long time ago so I do know its not hard and could wait til I was back in the usa. In fact I sat ppl, ppl h cpl and cpl h all on the same day - I was young and keen back then, but it shows the writtens are really not hard. Just buy the gleim book or look for questions on the web, and read the fars, sit it at your school after you have been in the usa flying for two weeks and its just an hour or two out of your life. The oral is a lot harder, and you can only prepare for that by proper study and immersion in the flying environment, but its the same sylabus, so dont fret about the written, focus on the oral and the written will fall into place. Besides gleim and the fars,the FAA have a good set of free publications, look on their website here
Handbooks & Manuals
Some stuff you just have to learn when you are there, like maintenance records etc, and some of it gets covered as you fly anyhow. Hope it works out for you.