In reply to ruai:
Depends where you're based, but you may find that securing a good instructor and some good weather are the decisive factors. That being said, N. Wales means you could be in Ogwen, in the Pass, at Tremadog or at Holyhead , etc. - i.e. places with distinct microclimates, giving you and the instructor more options.
Separately: find a friend who also really wants to learn and go together (so long as they can safely belay at a minimum). Instructor will probably find it easier to manage you in a pair, anyway; the cost will be similar; and you'll have someone to keep practising with.
The more you can learn before your course, the more quality you'll be able to get out of the course, so practise your knots, building belays in your living room and knowing what good gear looks like. It will help you to know what you really want from the instructor.