I managed to get an FAA licence on the back of my UK licence without leaving the country. After speaking to the FAA, I found out that they often (usually about once a month) have officials in the UK who can do the necessary verification etc. I met up with one in a hotel near Gatwick, we sorted out the paperwork and that was that.
I have since been to the States, done the FAA IR and it is definately the way I would choose to go!!!
The only thing to consider is the now very quiet DFT proposal to prevent foreign registered a/c from being based in the UK... but that now seems to have gone away, unless anyone knows differently!!!
PS - The trust thing is not a big issue. We use Southern but I'm sure the others are just as good!