Sorry I've only just picked this up, Pankers.
Thanks for the update. Yes, it does happen. Plumbing can be a bit of a black art. To be fair, small leaks are notorious for turning up after the plumber's gone home. Having said that, in your case it sounds a big enough leak to have been noticed right away. If in doubt, a quick return visit the next day might have been a good idea before re-flooring etc.
It's a thing with plumbers. Even the best ones can be a tad arrogant. Their repairs never leak!!! Mmmm, hasty words.
Knowing the pitfalls, I can only agree that this lot should have been better checked.
Glad you got to the bottom of it.