W
Waluigi
It was a half tongue in cheek comment but actually I do find it interesting 🙂
Why dont you contact both associations and ask them about their inspections and what they cover. If it wasn't in your builders terms I believe they can't insist who does the inspection. The tta probably won't cover the instalation of goods but to be honest the tiling is probably going to be the most expensive part to correct .
Just had a quick look and it looks like a genuine organisation. I also took a look at installers registered in my area and how to apply to become a member. An annual fee is required. If the company you have been dealing with is a member of BIKBBI (rolls of the tongue that acronym doesn’t it?! 😉 ) then I’d be a little worried there is a conflict of interest there.