The fact that the UK didn't have to stock up with a shedload of Dollar bills in the piggy bank first to pay for the thing may also have something to do with it, much like a lot of other buy British first selections in the 1950-70 (Mason and his ilk never look at the real reasons projects get selected or canned, like a planned piece of technology is found not to be possible within the time / cost schedules or there is a massive change of policy due to improved technology / Change of threat / Economic meltdown killing the rate of the pound v the Dollar (1956/67/73) / Etc). There is also the fact that the British requirements actually took the requirements of confronting an enemy using heavy ECM more seriously than the US did back then. As PrOOne states, only really the MRCA ADV (as it was then) and F-14 could meet the requirement and the F-14 wasn't value for money as regards performance v price tag.