Hello mate..........................
First off.....Oh Dear..........
Right, lets sort the gas issue out first.
He SHOULD of done a drop test on it......
If he is Gas safe registered then ring Gas Safe and say that you are not happy with Mr XXXX and there is still a smell of gas that he is not sorting out....they will be straight onto it.....
Radiators.
Sounds like he has added the rads in and not balenced the system out correctly......it needs to be balenced........
Banging pipes under the floorboards is because he hasnt sunk them deep enough and wrapped them in lagging/clipped them.......that needs sorting..
Bathroom
Sounds like the bath has been fitted and not leveled up, thats why the screen wont fit right.
All in all.........he sounds like a right prick.....i would not be paying him a penny till the gas leak/smell is sorted and the bathroom is sorted out.......
HOw is he making you look a cunt with the bathroom???........... Its not fitted right, full stop....you should be making him look MORE of a cunt