First, ask yourself why you're disillusioned with your current school, and whether or not this can be sorted by talking openly with instructor, CFI or owner - however intimidating you might find that to be, or otherwise.
Second, if the answer to the question is indeed to leave your existing school, ask yourself what you want in a replacement. Then you and only you will be able to select an alternative from the following list, and then only once you've visited them all:
Leading Edge (Cumbernauld) - C152's (or 150's, not sure which)
Glasgow Flying Club (Glasgow) - PA38's
Prestwick Flying Club (Prestwick) - PA28's
Prestwick Flight Centre (Prestwick) - a selection of types
Leading Edge (Perth) - Cessnas again
Scottish Aero Club (Perth) - not sure what types
If you want to include microlights then Strathaven isn't too far from Airdrie, although Balado might be.
Good luck