You were spot on Slug - it was a leak on the pipe from the street into the house - anyway I got a plumber in and he fixed in an hour. He also fitted a cut off under the floorboards because the council had poured concrete down the access hole in the street! wtf!! Unfortunately the plumber didn't...
I have a weird damp patch in my hallway and the constant sound of water running underneath. When I turn the water off at the mains it still carries on?
It sounds like a fast running stream underneath the floorboards.
I would call the landlord but seeing as he wont even send me a signed copy...