I recall quite a few FAA aircrews, including ex-Sea Harrier pilots went to the USA and were assigned to F/A-18 E/F squadrons, and more were to follow. I believe they were recalled/cancelled when the UK went back to the B.
I imagine there are a few FAA/RAF pilots on exchange with the USMC AV8B squadrons currently?
Would have been interesting to see the T-45 in UK service, but I do not recall it being looked at either.