http://www.faa.gov/licenses_certific..._verification/ appears a good place to start. Says you shuld send in the forms for verifying your licence at least 90 days before you intend to visit the FSDO. No idea on the costs at the US end.
At the UK end you need to ask the CAA to verify the licence. This involves sending them £38 and two forms SRG1160 (the verification authorisation) and SRG1187 (the payment details). Full details can be found at (details at
http://www.caa.co.uk/docs/175/srg_fc...n_process.pdf).
At least thats the theory... let us know how you get on.