Sorry, it's been an age since I updated this. I'm not sure where the last couple of weeks have gone, to be honest - I seem to have been working as usual, but the days have zoomed past and I lost track.
I do know where the last couple of days have gone, though, and they've been distinctly damp. During the week we'd noticed water dripping in our pantry (a long narrow space under the stairs) and thought we'd tracked it back to a badly-repaired joint in the main water pipe down there. By Saturday, it was significantly worse so we called out a plumber who banged and thumped and repaired the thing as well as he could (Saturday not being a good day for plumbing since all the builders' merchants tend to shut at midday). He left with profuse apologies for not giving us a permanent fix, and a promise to come back on Monday to finish the job.
On Sunday morning we awoke to find a pool of water on the pantry floor, and the ominous sound of dripping. Further investigation revealed that the joint in the pipe was bone-dry, which meant the water had to be coming from somewhere else - but where? It wasn't until I spotted a mysterious dark stain on the hall wallpaper that we realised the awful truth - it was coming through from next door. This takes some doing, believe me, since the party wall is nearly two feet thick. But coming through it was, and at an ever-increasing rate.
I gathered old towels, and sent Dave off on a neighbour-hunt. Our next-door neighbours themselves were away, but next-door-but-one had a key, and he and Dave went in to investigate. Seconds later Dave shot back, liberally sprayed with water, and hared off again with his toolbox. Turns out their boiler, which is in their attic, had burst, and water had quite literally been cascading down through their house for days. The men got the water turned off at the mains, which at least stopped things getting any worse. There was still an awful lot of water to drain away, though, and although it's slowly drying we've been left with a huge patch of sodden plaster in the hall, and a total mess in the pantry. It'll take weeks or even months to dry out completely and we're thinking of hiring a dehumidifier, to try to keep the damp, rot and mould at bay.
We're just grateful, though, that we discovered it when we did. Things could have been much worse for us, and a complete and utter disaster for our neighbours, if that water had continued to cascade...