Just out of curiosity did the join that the fitter came back and glued in front of you open up again ???
Sorry for the delay in replying. No, that joint didn't open up again.
Anyway an update:
I left several answerphone messages, none of which were returned, and have now written to them giving 14 days to respond. It was sent recorded to what I now know is the guy I dealt with's home address (he is the company director).
Their website is now down, but the error page pointed me to another flooring site on the same web hosting account, with the domain registered to the same address as the previous site.
I think they've started trading under a different name, although there's nothing posted in the London Gazette to suggest their original limited company is being wound up.
The new site has a different phone number in the same area code, but it belongs to a number forwarding company so it's probably just diverted.
The plot is thickening, unfortunately.