You don’t seem to trust my advice I appreciate that's up to you but I only do quality refurbishment work on bath/shower rooms & am also a plasterer; I do everything that's required (except the electrics) - plastering, tiling, plumbing, fitting out. I've no idea if your builder is charging quality prices but what he's doing isn’t quality & it needn't cost much if any extra, it's usually just a question of using the correct materials & doing it properly; the tiling subby is probably your builders mate!
Richard - you misunderstand me, I'm not mistrusting you at all, all my questions have been followups (at least I thought they were). Apologies if you think otherwise - you're advice is invaluable.
I'm just trying to figure what to do, as cancelling my loft build when it's 85% done is a pretty major decision, I think you'd agree, and has all sorts of implications! Plus, this wasn't a top price quote so I'm trying to figure out what's going to be 'good enough', and reasonable to expect these guys to do for the money.
I want to get this job done, so sounds like I should just get the plasterboard/floor tanked properly, only get the untiled section of the walls plastered (it's half tiled away from the shower - does that to-be-painted wall need to be tanked as well, or will water resistant paint be sufficient), and let the tiler do the tiling onto the plasterboard.
Once again, thanks for all your advice.