Is there any rules about the location of stop cock?

Other

Follow Virgin came and damaged my property, ( they drilled a hole on my water pipe and caused serious damage) now they have denied their responsibility by saying that my stop cock is not at visible place, it is between the wall near the gas meter, it is not visible but can reach. Also the pipe they drilled isn't a internal water pipe, it is the main pipe which supply the water upstairs. The stop cock for the main pipe is very hard to turn off and the valve on the street was broken. They said there's some regulation about cannot put the stop cock between the wall etc, therefore they refusing to pay my insurance company and declined my claim for my content damage. I have contacted Citizen Bureau but seems not getting anywhere, they ask me to go through Virgin complain procedure first. I didn't buy legal cover but I am looking into small court claim and other options etc. So is anybody know about this regulation Virgin on about, is there any regulation about can't put stop cock between the walls?
Thanks