Tim, the US does NOT give the UK full-up versions of its kit, as this testimony from the head of Qinetic to the PSC makes clear:
Exchange in PSC on DIS last week, shamelessly plagiarised from RonO on Warships1.com:
"Mr Ferrero: I think there has been in the MoD in the last five years a concept that somehow or other ultimately we can buy technology from the world market, that in reality we are so close to the Americans politically that they will always sell us anything that we really need. I think that the MoD has now come to realise, through recent experience, that that is not actually true. Even to their closest ally, the Americans, are very restrictive on the way they transfer technology, and systems we have purchased from the Americans in the recent past have turned out to be the "export version" rather than the real version they are prepared to give to the Marines or the Army or the Air Force. That reality will have to guide everything that we do in terms of technology investment in the UK.
ferrero is the head of Qinetiq so he should know of what he speaks.
There's also a further exchange that made me laugh my asss off. There's been a study comparing spending by countries on defense against the resulting military capability. The UK claims to get great value for money by buying cheaper equipment from abroad rather than spending your tax money in the Uk with UK companies with a Uk workforce. Turns out that there's no measurable benfit in doing that. France which has exactly the opposite policy is just as efficient. Gordo gets it wrong again."