Thanks for all the comments and questions.
Some answers:
The course costs around £1200-£1500. That includes everything - all materials, accommodation, food, tuition, spraying ... the lot. You can do it for less, by simplifying the design or using cheaper materials.
The glue joints are generally left, clamped, to set at least overnight and sometimes longer (ie 24 hours +). No real tension is applied to any of the joints until day 5 (when the guitar is finally strung), so it's had plenty of time to set properly. Both guitars that I've built have been rock solid, so there's no problem with doing it that quickly.
The guitar is generally ready for finishing by the end of the day 4. The paint sprayer then works through the night and the guitar is ready to finish (install the hardware and fret dressing) on the final day of the course. Obviously, this limits the range of finishes available - course attendees who want something more complex have to leave the guitar there for some weeks after finishing the course. Mine just has a clear satin lacquer applied - which is all I wanted. Some guitars are just oiled - there's time to apply 3 or 4 coats of oil and still have the guitar ready to finish on day 5.
The best bit ... there's no easy answer to that one. For me, it was the gaining the confidence that I could build a guitar. It didn't teach me "how to", step by step, but it did give me the confidence to get on and try it myself. I've done 2 more since the course (late March) ... and have learned loads with both builds, and will probably still be learning loads with each build even after I've built dozens of guitars! The guy running the course is an excellent teacher - calm, patient, friendly, and a real expert. He gives so much confidence that even if something does go wrong ... it can generally be fixed. That reassurance/confidence was probably more important than learning any technical skill.
And finally, I'll put some pics on the GOTM thread - thanks for the tip!