Airmen Certification: Verify the Authenticity of a Foreign License, Rating, or Medical Certification
What you'll have to do is get that form filled out and sent to Oklahoma City. I believe you may also have to get an FAA medical to send in with that form; not sure though. Once you've submitted it, I'd suggest you call to verify they've received it.
They'll get in touch with the CAA to verify your certificate, and then send a letter to you, as well as the FSDO you indicated on the form. By this time 6-8 weeks have passed.
Once you get the letter, you have 6 months from the date on the letter to go to the FSDO you specified. You must call the FSDO beforehand to make an appointment...national security etc.
You'll need to bring your FAA medical, logbook, foreign certificate, and of course ID. You'll need to fill out an 8710 form. You will meet with an inspector, and will be issued your temporary certificate. The plastic cert comes in the mail a few weeks later.
See
14CFR§61.75 for more info.
You'll be able to get single-engine privileges, not sure if your multi rating will transfer. You must carry your UK certificate with you while you exercise your FAA privileges.
Clear as mud?