I regret that my wife does not want to offend him and having seen two jobs done for friends of hers was impressed with the finish (of which I have no complaints). He has done 5 courses on two walls,which will stay put, but remainder will be done with cement based powder adhesive and an acylic primer. Fortunately PVA was only used on the short external wall. I know the tiles should all come off and start again, but I can do without another major barney with the Mrs and at least this way if they do drop off I am totally in the clear and can say I told you so !