In reply to BarrySW19: I've done various NGB courses at PyB and I certainly can't argue against the whole experience; good location, good instruction, good accommodation, good food and a good bar.
However, I didn't have much choice with my courses; it was PyB or Glenmore Lodge. You do. Any one of several hundred Mountaineering Instructors (or Mountain Guides) throughout the UK would be more than capable of delivering a 2-day learn-to-lead course to a good standard. For example, I often deliver leading courses at Swanage.
Most climbing courses are run (and hence costed) at a 1:2 ratio. So if it is just you who want to do the course there is a distinct advantage in going to PyB, Glenmore Lodge or another larger course provider. However if you happen have a climbing partner, or there is a group of you, who want to receive similar training, it will likely be far cheaper to go directly to an individual instructor. However, you would then have to make separate arrangements for food and accommodation, which may or may not be an issue.
People regularly ask for recommendation for instructors and companies on here and a comprehensive list of professional instructors by location can be found online
http://www.ami.org.uk/find-an-instructor