I work for a US company in the UK. Keep in mind that working for a US company and then moving here and working for the UK subsidiary does not neccesarily give you an advantage. (Note - I didn't transfer...which is a different situation and probably much easier if folks can go that route).
Anyway, before I moved over from the states, my former US management hooked me up with a project over here. The project was lead by a US based executive living in the UK for a 2 yr term, I interviewed with her and even came over for a two week business/gap session (while still employed in the states at that time). Shortly after I got a verbal job offer from her. Where the issue arose was with the UK human resources department. One of the HR managers insisted that my manager "post" the position AND interview other candidates even though she wanted me for it and my salary would be picked up by the project budget (based in the US). I also had to come in and interview with the HR manager. During the interview she said "as we sit here (X - my manager) is interviewing someone for the position...you know, we had to make sure we couldnt find one of "our own" for the position". I looked at her and said "well, I work for the same company....its just the home office in the states". Her point was "a British" person. (The irony was I knew my manager was interviewing a guy that day because she told me about it....I thought it was a bit harsh for the HR manager to be so blunt about it). Anyway, my manager went through the motions of the other interview and I went through the motions of the HR interview. I utlimately got the position and after all was said and done....it was a month of basically sitting in the house stressing over how it would all turn out. Not a good way to begin things...but I soon got over it on my first day on the job.
Anyway, just my little story on working for a US company in the UK.
Julie