Anybody use G & M Plumbing Contracting?

I am an architect with a project in Windsor Terrace. A friend of a client recommended G & M Plumbing Contracting to my client. Has anybody used them? Their budget square foot number was incredibly cheap, and I generally subscribe to the idea that if something looks too good to be true, it probably is. So it really makes me wonder when a contractor gives me numbers 33% lower than what I’ve been told to expect.

Anybody heard of these guys?

Thanks