Not sure if you can train for the FAA IR in this country but here is the official word on the requirements for flying/training in the US:
http://www.awp.faa.gov/fsdo/foreign.htm
Basically aslong as your JAA PPL and Medical certificates are current then you will NOT be required to take any theoretical/flight training. Apparently you just toddle into the nearest FAA office and about 20 minutes later you have a temporary FAA airmens certificate. You even get sent a proper FAA airmens certificate to your address back in the UK. All for a small fee. It just once again goes to show how much the CAA seem to rip you off.
You cannot use IR priveleges on a UK reg'd aircraft, just IMC. You'll have to find a club that has a N reg'd aircraft (which I recall seeing someone post that they do exist in the UK for rent) to exercise full IR priveleges.
I have to stress, these points may be wrong but I did spend some time looking into it and a number of sources said that the above was correct.
Regards,
Simon
[This message has been edited by Simon W (edited 19 June 2001).]
[This message has been edited by Simon W (edited 19 June 2001).]