Everyone will have different opinions on insurers so shop around for yourself and compare all the prices, as RB says above prices can vary even for a 125, cheapest for my 125 was £120 a year. If you have an older bike you used to be able to get 'classic' insurance which was cheaper still but no idea if you still can get that. Make sure you read the Insurer's small print and terms and conditions. As Ragnar says it is all to do with if your bike is in/out of a lockable garage, and the area you live in.
Good luck with the CBT too, practice all the manoeuvres as much as you can before doing it and you won't go wrong