Good thing about the FAA licence is that it NEVER expires. However you will need to pass the BFR. This can be done in the UK (no TSA or visa etc needed), but you are like myself, have not flown for years and will need a "lot" of training before the sign off.
In theory it is only one hour ground and one hour flight with an FAA CFI, but you will have to know all the current (American) regs FAR/AIM 2008 and all other ground school stuff as well as in reality being able to pass your "check ride" again - GFT for the EU lot.
Willow Air in Southend do a lot of FAA stuff and Weston Air at Thruxton have an FAA CFI (Peter Metcalf) but I think there are many others. Also remember the FAA Medical - see the FAA website for AME in UK.
Good luck mate - I'm going to be doing my BFR soon after a LONG break also.