I currently get my breakdown cover through Saga because I was offered a good 'combined deal' with my vehicle policy but, prior to that, I used Autonational Rescue for many years. They're cheap and they provide an excellent service:
http://www.autonational.co.uk/
Chris
PS: When I used to deliver vehicles for a living, the company which I worked for used the AA to provide breakdown cover. I had a vehicle conk out on me on a road called Basing View, in Basingstoke. The company called the AA but their operator then phoned me to check the address. I gave the name of the road clearly but she said that it didn't exist. I then spelt the name out for her. She still said it didn't exist. I stood next to the road sign and read each letter out, one by one, phonetically. Again I was told that the road didn't exist. She asked if there were any local landmarks that their driver might recognise. It was then that I told her that the vehicle was parked on the car park of the AA's headquarters on Basing View, which she was still refusing to accept as a valid address!
;-)