I’ve not been onto this section of the forum before now so I have only just seen this thread and I have to say I am really shocked at the level of workmanship for your bathroom Rich!
It should make no difference where or for whom the work is being carried out, those sort of standards should have gone out with the Ark! Kezo seems to have highlighted lots of the problems but to be honest there are so many that it would take forever to list them!
The tradesmen involved should be ashamed and you are right to say that you will refuse to sign off on the job. Personally I would have kicked them off the job completely by now and have asked for a different contractor to come in and rip the lot out and start again.