We had a wet room installed in our upper ground floor flat (in autumn) and there has been a breach to the tanking in addition to several tiles cracking and lifting. The leak then led to the plaster ceiling underneath falling down - just before NYE. Our builder has offered to fix this but we are concerned about the job he has done overall, and would like to have the job looked at and fixed by a specialist. Does anyone have any urgent recommendations? Thanks in advance!!!!!