There was a similar thread a year or so ago regarding Ghd.
As for the college style program, in the UK kids end their schooling with GCSE’s. Most move on after that to Yeshiva or sem. In Ghd the schoolin system ends there. In Manchester there is an option to further that education to “A Levels”. The sems (New Ghd & new Manchesster) offer courses that give qualifications. It is possible many of these courses are in conjunction with colleges and uni’s.
From my experinces there, I reccommend you go see the place before commiting yourself, especially if you come from the USA as there may be a major culture difference!
Good luck with your decision