I would like to recommend leading edge as a former ppl student they offered me excellent instructors and availability, well maintainained aircraft with reasonable rates! They also encouraged unlike other schools not to pay up front but after each lesson. Although I cannot comment on there finances all I can say is leading edge seems so be growing stronger and stronger with the aircraft online booking pages never been busier!
I have also done training at pretwick flight centre for my night rating and again experienced high quality training, well maintained aircraft and the advantages of flying from a controlled airfireld would be a plus point for a wannabe commercial pilot.
There is also the new branch of BAT at Cumbernauld which has undoubtably one of the nicest and my personal opinion one of the best cfi's you will find, so that could also be worth a look!
Having personally or known people who trained at these I'd say you can't go wrong
Leading edge
Prestwick Flight Centre
Prestwick flying Club