I looked at the Ombudsman website and it only really seemed to mention cases where you're disputing your claim, rather than my case where you have a (big) problem with the premiums. Will definitely investigate more. I've just started work, so don't have as much time on my hands (great timing, not!), but I'll try to formulate my plan of attack.
40% would have been a reasonable increase, I think, but this could not possibly be described as reasonable.