We have used 'The Renewable Energy Academy' up in Durham, it's run by the same people, could not fault it.
It maybe doesn't go as deep into all the nuances that the C&G will, however the 5 day course, complete with tests does cover all aspects.
I have no hesitation sending all our guys on it. Two of our sparks did the NICEIC courses and when all the guys compared course notes, materials, what they'd learnt, the REA stood out head and shoulders above the other courses.
Coming back form an REA course the guys were able to survey, design, specify and install a system (still a lot to learn obviuosly !) they guys on the other courses we used simply didn't have the breadth of knowledge or confidence.
That's our experience, we are more than happy with them, be interested to hear other peoples experiences.