Glasgow has a lot of really good instructors, but the problem is price. I believe they charged £24 per landing which is a lot of money! (Typical BAA!)
I would maybe look at Prestwick Flying Club, Cumbernauld Flying School, Highland Flying School or Tayside. HFS is probably the cheapest, Cumbernauld I wasn't impressed with and PFC is a cracking place but a wee bit pricy compared to HFS however the experience of the instructors is top notch, guys like Stuart Hill, Steve Maric are top notch guys.
Stuart is the CAA Examiner at the moment, but he used to be an instructor with Prestwick BAe (Know known as Flight Training Europe) and was a training captain for BA Express. Stuart hill, the CFI, currently flies for FlyBE as a Captain at the moment I believe on the BAE 146, top notch guy knows his stuff very, very well.
There are a number of other flight instructors at PFC who are top notch as well.