I would not recommend GBW Plumbing..! They fitted a radiator for me and blew all the plaster work out of the wall and the pipework was disgusting.
Just out of interest, did you ask for it to be put right? and if so was it actually GBW or a sub-contractor? If you have issues I would look at website and contact them.
I have used them on 3 occasions and am waiting for job 4 to start soon, always polite, always clean up when done and really happy with everything they have done so far.