when i was instructing, i always dreaded PPLs coming in who had learned in the states. (almost) always needed a huge amount of remedial work to get them up to standard.
this isn't true for everyone of course, but i would say most. its a common theme among the flying community in the uk.
the US style of flying is so laid back compared to here, and as a result, coming into the more regimented and structured uk flying world is a shock to most. (and their instructor)