We had this once last year. I was told that someone would ring back in 1/2 hr. Ours was the electricity. I'm still waiting for someone to 'phone back. Luckily we have a neighbour who is an electrician. It does make you wonder just how reliable these so called 24hr. insurances are.
I hope he has solved your problem and that you will be leak free now.

Hugs, Judith.x