Answer: -A local plumbers merchant might give you a list of reliable plumbers - though perhaps one would need a recommendation for a plumbers merchant! Or if you're an AA member, they are reputed to keep lists of reliable local tradesmen. Also places like Homebase have cards in their stores. -Three years ago I had the same problem. I looked up the Yellow Pages advert of the Institute of Plumbing, which is the professional body charged with maintaining high standards in the industry. It's affiliated to the Engineering Council. I chose three members and asked each to quote for installing a new CH boiler and a new bathroom suite including shower mixer. Having established the professional competence of the three, I was happy to accept the lowest price, particularly as the plumber in question seemed intelligent and capable when he visited the house. He was also Corgi registered. Unfortunately what followed was a 4-month nightmare, trying to get a 2 week job done. The incompetence of this man and his employees/subcontractors was quite unbelievable. The boiler didn't work, the hot and cold systems were reversed (yes, hot flushes in both WCs), we were without any means of providing hot water for a period of ten days, several pipe joints leaked and one needed refixing four times, servicing valves were fitted in inaccessible places, the shower mixer was fitted upside down and failed to work ..... and more. The one thing he was great at was demolition.