jamie9456,similarly to you I often get very thirsty on the planes and I prefer to always buy a bottle /grab one from the lounge.In some airports it is impossible to get it onboard due to the security layout (eg:VIE/KUL).

So when leaving these stations on RJ flight I always ask for a big bottle,and never had a problem obtaining one from whatever galley-J or Y. Sending a pax to the a diffirent part of the plane to get water is ridicoulous. It's not even about entitlements,it's simply about common sense,which SOME BA crew seem to be lacking.

I was once flying LED-LHR in CE. The old LED terminal (not in service anymore) had security just before the gate,so no liquids allowed onboard . When asked,I turned down the meal,but asked about a bottle of water and was refused. I therefore had to ask the crew member to often refill my glass. What a waste of time and nerves!