MACH2NUMBER
The F-15 wasn't the aircraft it became when the aircraft was looked at for the UKAD role, while the F-18 was very much a paper aeroplane based on the YF-17 at the time the MRCA was finally selected. F-16 couldn't meet the OR period. F-14 was really the only viable US option and even then had issues. Giving development of the AI-24 to GEC was a big mistake, that job should have gone to Ferranti (Edinburgh).