I did my A2 C of C with UAVHUB. It cost £99 less 5% discount via @ianinlondon 's YouTube channel. Ian is a GADC member and experienced pilot who has a channel with some very helpful drone videos - well worth subscribing
UAVHUB is fronted by Matt Williams - another person who visits GADC on a regular basis. The course includes the cost of the mentored exam. I have given an idea of the course in the A 2 CofC courses thread. The general consensus seems to be that it the best course around
You can have a free trial of the course, taking you up to the mock exams then pay your £99 to unlock the mocks and the exam itself.