Actually, the military relationship between the UK and the US these days is 'they design it, we get it working properly'

Most of the tracking and targetting software used to be hard machine-coded onto Eproms which gave standard output to visual displays. It wasn't as pretty as some things, but you don't really 32Bit colour depth and 1600 x 1200 resolution for a radar display, as long as the system itself knows exactly where the plane is, a 'dot' is sufficient.
Also, hard-coded systems are a damn sight faster than going through some kind of 'portway' like W2K, with less chance of corruption. When a command has to pass through a load of non-user 'verifiers' it runs this risk of failure or misinterpretation, both of which could be disastrous

I'm sure people remember the 'feet and metres' incident during WW2 where troops got shelled because they gave range in Metres, being European, but the British artillery assumed they meant feet, imagine that on a Nuclear scale
