CBT for me was £80 in about 2001/2002.
DAS - My local place do free winter retests if you fail first time and the cost can be between £500-800 for a week course +
My advice, do your CBT and ride around on a 125cc for a while and establish yourself with some decent winter gear. Whilse doing so, get some one on one lessons in to get a feel for the bigger bikes and talk to the instuctors on whats the best route for you.