Cf,
My advice would be to think about what and how you plan to fly once you have your PPL(H). It is more important to be familair with the helicopter type that you will fly than the type of plank you fly. The stick-poling and hand-eye coordnation required to fly a hele well are greater than for a plank (IMHO anyway). If, as someone suggested, you may end up flying an R44 SFH, it might make sense to go and fly one in the US or elsewhere. It would set you up well for SFH. If you fly a (slightly) bigger hele, make sure that someone shows you how to fly it when heavy - a heavy R44/light R44 are very different.
I would normally advise that a new pilot learns in the UK if he wants to fly there, unless his personal circs make it much cheaper to fly in the US (e.g being there on business anyway). However, as you already are familiar with the UK, this is less important for you. You might want to learn here for other reasons though (like keeping UK instructors in work!)