the law and gas bottle storage

hi, we went to look at a second-hand caravan today with the shower/toilet, rear kitchen, etc... in it and when we were looking in the front boot we wondered were the gas bottles were, so we followed the gas hoses, (one going both sides of the van) and to our surprise, shock and horror there was a large gas bottle on each side hidden in the bedside cupboards with no ventilation at all and there didn't seem to be any cut-out switches on them. as this van was at a dealer we went inside and said to them nicely that we thought it was illegal to have the gas bottles inside and they should be careful as if someone had an explosion that they might get sued for selling it, she was about to get on her high horse but then just said, oh thanks for telling us, you could tell they wont do anything, she only said thanks to get rid of us, but we worry about the poor suckers that buy the van and they might not know that when laying in bed right next to their head is 2 bombs.
so is it against the law or is it just common sense?
Chris.