Kae and myself have now been to the supermarkets we know of in Glasgow and Edinburgh. The ones listed under Food & Shopping on this site home page now include Chung Ying in Dobbies Loan Glasgow. They all have a good stock, and the only Thai owned and staffed is the one listed as Nittaya Thai Market in Dalry Road Edinburgh. This one has changed name to thai@haymarket.
For value for money, Chung Ying Glasgow is certainly the best. It is a medium size Cash and Carry and supplies to restaurants and take aways, but is open to the public too. It doesn't take credit cards, but then that keeps the prices down too.
We don't know of any others at this point, but this is the one we will shop at for the most part.

Dave and Kae