Our Man has gone, and hopefully so has the leak.
The two rooms adjacent to the leak, one of which is the kitchen, show no sign internally of any damp at all. When we had these rooms decorated we made sure the external walls were lined with a damp-proof plaster board. It has worked very well. The good news about that is that the internal decor is undamaged. The bad news is that we didn't notice the leak for quite some time.
The leak hadn't gone and we called the same guy out again. It turns out there were two leaks that he fixed. In total, we had 4 leaks, all from different pipes/appliances within about a metre of each other over the space of less than 2 months.
1. One of the feeder pipes to the shower pump in the airing cupboard started to drip. I first noticed this when standing at the kitchen sink and water landing on my pate. This was the most trivial but the only one to cause damage to the decor. I still haven't got it fixed and we have been coming downstairs for showers.
2. Something mysterious that I thought was the boiler. Subsequent investigation showed that the heat exchanger was indeed leaking, but intermittently. I had found some small puddles in the boiler cupboard. The heating guy did find a problem with the boiler and cured it, but it was several hours after he left that I sent him photos of the leak. He diagnosed leaking heat exchanger.
3. A crack in an ancient lead pipe under the floorboards of the airing cupboard. Guy from AquaKare (South Ockendon) came out and fixed it. Impressed with his work.
4. After AquaKare Guy had buggered off, I thought "There's still a leak here!" The hot water tank had emptied itself of hot water and the outside wall looked wetter than ever. AquaKare Guy came back and found another leak, which I am convinced was caused by central heating guy drilling through a pipe when he fitted the boiler. Put in a different bit of pipe to bypass the one embedded in the wall.
To cap it all, the immersion heater decided to blow a fuse in the Eve plug with which we control it. Haven't got that fixed either, but we won't be needing it for a few months now that the sun is getting higher in the sky and heating the solar panel.
I've just had the bill from AquaKare. Cheeky buggers had included two callout trace/detect charges at £495. I phoned up a few minutes ago expecting a battle but the Main Man instantly agreed to send out a new invoice.