There does seem to be quite a bit of leeway in what you can wear. For example:
http://www.hambletonleisure.co.uk/in...rules-guidance
◾Swimmers must wear appropriate swim wear e.g. no cut off jeans or thongs.
So no bare bottoms, plus no exposed genitalia and I would guess for women - no bare breasts.
What could a pool attendant say to you anyway? 'Sir, I must request you to leave the pool on account of your brief swimwear'. You could then reply, 'Will you be throwing out that girl in the bikini, then? Or do you seriously think my bare legs are more erotic than hers?'