I don't know of the exact figure but as Heathrow Director said, it costs an arm and several legs and isn't easy either. Not that training to be an ATCO is easy by any means!
There is a recent post on here (titled, Stuff you NATS, I'll do it myself) discussing self-funding and whether there is any chance of finding work after self-funding,
Seriously though, the others are right. In the first instance, if you really want to be an ATCO then apply to NATS. NATS controls UK en-route airspace and is the only company that does so. NATS also holds contracts for all London airports and in Scotland, the North, Ireland, Wales, the South and South West. They will put you through a rigorous recruitment process where you will be tested, tested some more then tested again, but that will also give you the means to find out if, at this moment in time, you are suited to the job aswell.
I hope you find what you are looking for and good luck for the future.
