Hi Molly!
I've heard about the situation in Glasgow and it must be a real pain in the arse - I know there are plenty in Edinburgh but that won't help you if you're not allowed to work for more than one and you need more shifts.
The problem with looking due south of Edinburgh is that brothels are not tolerated anywhere much the length of the North East; there are a few agencies with incall flats that ladies on here have mentioned (none particularly favourably) but parlour wise, AFAIK, there is nothing at all until you get to Hull, which I daresay is further than you meant. There are a couple in York and a (very) few in Leeds.
Could you travel from Glasgow and try the North West side? Things are different there, and there are some well thought of places (as Emily said, look at the FRs) which could be worth your while travelling to if it's only a couple of days a week and they're consistently busy.