Nasty plumbing situation

We've finally manaaged to coax a plumber out to the house to help trace the leak in the central heating system. The first thing he told us was that he'd spent his first Christmas in this house - at which point I decided to limit my comments about the people who undertook the barn conversion.
Anyhow, we have a leaking pipe right underneath the bottom of the stairs, and the water has probably spread right underneath the hall flooring, so it's a mess.
With luck, the tradies will be back next week to fix the leak ...