It was Basil Fawlty who turned it into a catchphrase - "Can't we get you on Mastermind Sybil? Special subject the bleedin' obvious" and it runs through my head every time I see one of those notices about warm weather at a tube station. You probably know what I mean - "To avoid discomfort in hot weather carry water" :that sort of thing.
So are there drinking fountains at stations? No
Do they sell bottled water at stations? No (there might be a kiosk at larger stations but not as a rule)
Bleeding obvious? I should say so.