LT you open up an interesting thread within this thread which is more dedicated to the Royal AirForce Officeer and Aircrew Selection. Although you are therefore off-topic may I say that the UK has a college that is both similar and different from the US concept.
That is Welbeck 6th Form College.
http://www.welbeck.mod.uk/after_welbeck.html
Interestingly, when you look at Welbeck on the internet it seems a bit schizophrenic.
It is an tri-service defence sponsored college and theabove site carries all the Services' logos.
Confusingly other Google hits suggest a different ethos:
The
British Army's Sixth Form Residential
College for students interested in combining academic with sporting activities, and a future career as
an Army ...
www.welbeck.ac.uk/ - [I could not get the link to work]
It is clear that this PURPLE organisation is very much a GREEN shade of purple. http://www.dsfc.ac.uk/