humbug said:
The question now is what do we do?!
Firstly, well done for confronting the
overbearing one. I know it can be a hard thing to do. So you did well, especially in withholding payment - that's puts you in an excellent negotiating position.
In essence what you have to do is make a list of all the things that aren't satisfactory - damage, unfinished items, incorrectly installed pipes, etc. It would be a good idea to get a heating engineer in to check the work - chances are there are many shortcomings, even illegal aspects.
For example, is the boiler a condensing boiler? Are there thermostatic rad valves and a room stat installed? Has the system been properly flushed and commissioned? You could post a photo of the boiler and pipework around it for our comments, but an on-site inspection would still be valuable.
You will end up with a list of all sorts of remedial works required, which will cost loads. Then you must decide how much you realistically need to deduct from the bill to gain reasonable compensation. Consider how the
arrogant one will view it - 10% loss he might shrug off, 20% maybe, 30% or more he would probably fight against. So be pragmatic about what deduction you will ask for.
Then make a written offer to the
insensitive one, listing all the faults, damages, etc., and offer a certain figure in "full and final settlement" of the account. If he accepts this, pay by cheque and make sure he signs a statement that he accepts this as full and final settlement. If he doesn't accept it, inform him that you will seek a deduction of the full amount of damages, etc. if he takes the matter to court.
Chances are that the
domineering one will accept a quick settlement, albeit with a lot of huffing and puffing. Remember that holding the money gives you the whip hand, so it's your turn to give him a taste of his own medicine.