Feeling rather silly at the moment. Last night I adjusted a radiator and found a leak coming from a very old valve. Fearing the potential consequences of me tinkering with it in the middle of the night I wrapped towels around it to catch the leaking water and called the plumber this morning. It turned out all he needed to do was tighten a single nut and the problem looks like it's resolved. D'oh.... I could have done that, if only I'd known how simple it was. He didn't even charge me (he's a local guy who does assorted jobs for me).
He's been a real blessing, being willing to share some expertise in and around doing a couple of paid jobs for me. I think I need to buy him a case of beer for Christmas, as a thankyou for all the assorted small stuff he's helped with and not charged me for.