Its a cycles requirement, x-amount of cycles in y type of aircraft, ie turboprop, or jet determines weather you will be a wide-body FO, narrow body FO, or a cruise officer. Yes, the JAR ATPL's (yes plaural) are required along with the kicker, the right to live and work in the UK. Good luck with that one! Would be pretty sweet to check on to New York tracon with a 'speedbird' call sign!
Cheers!