Quite an interesting thread, but no doubt for the
tiler and very embarrassing one too.
No matter what the
tiler quoted for the job, has no bearing on this matter really as he was obviously happy with the agreed amount, and I fully agree with the price reduction regarding materials too.
If I had any work done in my home, and I had a genuine reason for complaint regarding quality, then I wouldn't be inclined to pay full costs without the problem being fixed at no extra charge.
Good luck with it.