Yes you can revalidate the FAA IR by experience....essentially as long as you have met the requirements within the last 6 months then you are good to go. Go over 6 months and you have a further 6 months to meet those requirements in VFR conditions (i.e. using foggles etc. with safety pilot). After this 6 months they you REQUIRE and IPC before you are current again. IPC can only be done by an FAA CFII and you get a logbook endorsement.
What I do when I go to the USA is kind of combine an IPC / BFR for a bit of refresher training, then on my return to the UK reapply for the IR(R) based upon this IPC. Or if you happen to know a friendly FAA CFII in the UK of course they can do all of this too, and if you don't pay them then you don't need a DfT permit for your aeroplane (now CAA I think?).
The wording from the CAA is along the lines of:
If you hold a foreign IR then you are exempt from the ground study for the IR(R).
If you have had an IR test or revalidation (inc. IPC) within the last 24 month then you are exempt from the flight test for the IR(R).
You just fill our the rating application form (& fee) and send together with your FAA certificate and logbook showing the IPC flight and endorsement.