In reply to jeed: The good news is that pretty much all the providers do a decent job these days. There is also an excellent online training course search facility
http://www.mountain-training.org/find-a-course
However, if you want a firm personal recommendation of instructors I know I can give you two:
Look at Peak Mountain Training -
http://www.peakmountaintraining.co.uk/ - which is run by three exceptionally experienced instructors.
It is also worth contacting Paul Smith. As well as being a UKC regular (Paul at work) and author of several highly regarded books for instructors he is a very experienced CWA/SPA provider. He doesn't advertise widely but always runs several courses in the Peak each year. His contact details are on his website
http://www.rockandwateradventures.co.uk/