No worries. The international pool has a gym downstairs too, I think you can get a membership or pay per visit - but it's not as swanky as the private ones in the changing areas etc! The international pool is OK (cold!), there are normally some lanes for club training etc and some lanes for other people, but I've only used it a couple of times because my gym is just over the road and far quieter. Plus you get towels
I would have thought that the student gym will work out cheaper than the others, unless you go with an off peak membership maybe - even if you paid £1 per visit and went every day you'd pay less than I do for my monthly membership fee (but that's the peak time membership).