Morning John.
Nat was concerned that taking the complaint to the company and stop work might make them not hand over the goods she's paid for from them.
The suggestion/thoughts of writing off the tiles i mentioned more as a bargaining chip if they demanded any labour for what they've done. But your right, ideally they should refund there costs as well or supply more tiles.
Judging that the bathroom is not complete Nat and therefore not being used. My first guess is any leak will be on a feed pipe rather than a waste. Therefore a continual leak. Any idea where it maybe coming from Nat?
More to claim against them for damaged ceiling if they have caused leak on central heating pipes!
Stop all work if your not assured it is being completed to British Standards and in a professional manner and demand a full refund.