Member charged £5 to fill up with water

I'm a member of the Caravan Club and a proud owner of a Burstner motorhome, I tried to book on a club site however I was told they were fully booked.

i wanted to stay in derbyshire so decided to stay a few nights on a pub carpark, 

i needed gas so I called into the club site paid £20 for a bottle of propane and left, the next day I went back to ask if they minded if I filled up with water as a member iit was told its not normal practice to allow non residence to  have water pans they charged me £5. 

surely as a member what can't you allow motorhomes to fill up with water, I will not be renewing my membership if this is how you are made to feel by our club,

please can members give me there thoughts on if you think it is fair that our club won't allow it's members to fill up with water at a reasonable cost.