I stand to be corrected, but the salaries for ATCOs going to Swanwick are roughly just under 15K for Student ATCO, 21.5K as a T&D at Swanwick, 27K upon first validation and 39K upon promotion to the ATCO 2 scale which occurs on the second anniversary of your graduation.
You get a lot less while at the college nowadays but it goes up quick if you are successful.