ATCO2009... Have you read CAP670 or "THE UNITED KINGDOM AIR TRAFFIC CONTROLLER LICENCE, A GUIDE TO THE LICENSING PROCESS" ?
I guess some people on here will be curious as to why you are spending an arm and a leg instead of trying NATS first? The Air Traffic Controller's Licence is similar in many respects to the higher commercial pilot's licences - several of the same subjects, similar amount to time to become "solo" (ie several years) and similar pass marks required - at least 70% plus regular competency and medical checks throughout your working life. Irrespective of where you do your approved course, ultimately it will be the CAA which issues your Licence and it becomes your personal property.
Incidentally, I presume you have a Class 1 Medical? If not, it's time to think also whether you are fit enough..
I wish you all the luck and I hope you are prepared for some very serious work ahead.