Preswick flying club gets my vote.
Not only are the instructors all commercial pilots but also they are some of the nicest approachable instructors about. They don't bother with any of the strutting about stuff.
In fact it was only after discussing the club with my caafu examiner, that i discovered that my instructor was not only a QFI in the RAF but was also a test pilot. And he also said that he had seen ppl's come out of Prestwick which could have sat there CPL and passed no problem.
PIK is great for training nice mix of commercial traffic with periods of calm if you need to do circuits. The tower are very friendly and can usually be found in pprune chat about 10pm.
MJ