Thankfully the problem has now been resolved. My customer sent letters to the chairman of B&Q , the Jobsworth at the Southend branch, and customer relations. Explaining the problem. They have now agreed to change the cistern. If it had been me I would have demanded compensation for the inconvenience caused., but hey Ho, be grateful for small mercies. Thanks to those who commented. I've helped to fit lots of bathrooms over the last few years, most of which have been supplied by Bath Store. Never had any big problem with them. Minor problems usually put right in a day or so.

It's a ceramic cistern, with ceramic hand basin which fits in the top of cistern. The hole does look as though it has been made after casting, there is no glaze around it, and some of the surface has shelled out. Why anyone would drill a 42mm hole in the bottom of a cistern is a mystery to me, and it's the first time I've seen it done, in over 40yrs in the trade. The one in store has the two standard 20mm (approx) holes.

This not so much a problem of mine, but of my customer. He asked me to fit a new WC suite for him, it's one where there is a small hand basin built into the cistern lid "A Duet" On opening the box up and starting to put it together, I first noticed there were bits missing, and that one of the holes in the cistern was oversized. Although I didn't know this for sure until later. I drove to the B&Q store (5 mile round trip) , managed to get the missing parts, and see that the cistern we had, was indeed faulty and was told that if it was taken back it would be exchanged. My customer returned shortly afterwards, and instead of seeing the person I had, met a rather officious jobsworth. Telling him that they had never had a problem with these before, and that someone must have drilled it out, and they wouldn't change it. Despite having one on the shelf which they can't sell as there are fittings now missing. He has phoned B&Q head office and been told they will have to refer back to the branch. Where they will undoubtedly repeat what they told us. The next step seems to be Trading Standards as the supplied item is not fit for use. Unless anyone has other suggestions ?