Its a bit harder explaining the order of everything thats gone on in a few words on a forum and I'm a homeowner not a professional, but just to summarise for now the job has progressed well bar the one big issue of how the wall tiles have gone on. Its not ideal, but its an honest mistake that we now need to get put right. My original question about whether the tiles will dry out has I think in all likelihood been answered and it seems that the only course of action is to replace the tiles. I'll report back when there's more to say, but thank you to everyone so far for your useful advice.