How much does it cost to plumb and pipe a 4000 square foot house?

Don't pay any more than 4-5 thousand pounds (labour only)

A big house is no harder to do than a small house.

No matter how well you know the plumber, get it in writing what stage he takes the Plumbing to. First fix- all pipe work and boiler and tank. second fix /radiators bathroom suite ,kitchen sink, outside tap.

Also can he sign it off and test the performance of the boiler after installed, If not ,that will cost another 200 quid.

I got stung for a second bill after paying his first bill for 1st &2nd fix. A so called '2nd 2nd' fix which was for fitting a shower and bath. So be careful.