I have had a gym membership with Freedom Leisure for years, they run the council gyms in Brighton and Hove. It's a bit expensive at £55/month vs £20/month for pure gym, but they are closest to my house.

I never found a discount until now. I have had a dormant WaveCB bank account for years, I used to use it for discounted bus passes.

I couldn't get them to honour the 15% discount, but they gave me 10%. That's an improvement.