Well I called the lady on the Tue night and explained that I'm not prepared to tile the floor how it is and that it all has to be taken up and done again. She agreed after I had told her about the problems she would get if I did tile it.
I have not been back since as I am going to wait for the floor to be re done and then visit the site before I go back to check it is all correct.
"I have checked out you concerns with the Co I purchased the tanking from they
have confirmed the following and sent Data sheets to confirm
Red membrane sheet is coated and therefore should not be stuck down with adhesive
but laid loose and edges sealed with tanking paint.
Also the thermal board under the heating cannot be placed under the WC it needs a firmer
board due to the weight of the wc which would crush the standard thermal board.
Th electrician has been out to the flooring and assured me that the mat will not burn out
Obviously the above goes against all the concerns you raised, I want the tiling to go ahead on the floor
and take full responsibility therefore should the floor fail and the resonsibility will remain with me."
Personally I wouldn't touch it. Regardless of what they say you'll be in the firing line when it goes wrong. Get paid for what you've done, leave your contact details and when someone else does it and it goes wrong you can you and do it again from scratch the way it should be done!