Yeah, it's an absolute nightmare trying to find flats at the moment. However, if it's a flat for next year that you're after, a couple of the estate agents on Byres Road are making up a database of students who are looking for flats next year, and then sending out details of all suitable flats (from the tenants that'll be moving out at the end of the semester) in the next month or so, so there should be much more of a selection around about then.
I'm looking for a 3 bed flat at the moment, and the cheapest I've found is about £220 pppm. But I agree that rent in the West End is absolutely ridiculous!!