ATC College
I've been to both the NATS college in Bournemouth and the Bae college in Wales.
My advice is that the college is unimportant, if you really want to be an Air Traffic Controller you need to go where ever is needed and take whatever **** they give you to get that yellow license. There is only one person who can get you a license and that's you, not your intructor, mentor or course mates.
If it's what you want to do get your application in to NATS or try to get a job as an assistant at a regional airport. Local (non NATS) airports sometimes employ local youngsters and train them as they are more likely to stay. My employer uses the NATS apptitude tests and interviews for its trainee selection
I'm not sure paying for your own Aerodrome endorsement will get you any closer to being employed as you're still unproven and will only have obtained a sizeable debt. If anything being an assistant first will help improve your technical knowledge and be more useful.