Just an update for posterity. The Astra is no more. A second chap who is very transparent and has a good rate on his labour undertook to do the head gasket, and to redo the timing chain because the previous original MUPPET garage had cheaped out and bought the kit that doesn't include the cam sprockets - so the new chain was slapping about on worn-down old sprockets. £650 down the drain. New mechanic was also horrified that they charged £650 for the timing chain job, and that they didn't just plough on and do the head gasket at the same time, since it's only an extra hour once you're that far in. Anyway, he got in there this time and #2 piston is about 1mm smaller than the cylinder, you can literally see down the side of it. Covered in coked up deposits from burnt fuel. Head gasket has clearly been on the way since before I bought it. We pondered 2nd hand engine and new chain kit on it - that'd only be about £800. But then he checked the undercarriage and found: a broken rear spring, two weeping rear shocks, corroded brake cable mounts, a badly corroded exhaust mount and rear bushes that had cracked long ago, been siliconed up by some cowboy (first garage is my guess) and had cracked again. Another local garage gave this car a clean MOT and an 'all clear' on visual inspection for me not 4 weeks ago. Needless to say I'm not happy with them about that. Windscreen also has a chip, so all in - bushes, shocks, springs, windscreen, engine, chain kit - you're talking £1200 or so. **** that. The current mechanic said "we can do it all if you really want, but the car's only worth £1k after all that's sorted, and you can get much better condition used cars than this for £1.5k, so if it was mine I wouldn't bother." I thanked him for his honesty and let him scrap the vehicle to cover the labour costs. One important distinction this whole experience has taught me is: when you go to a garage/mechanic, note whether they have plenty of indoor storage space or not. Garage 1 had none; consequently they were rushed, tight for space, and reluctant to stop a job halfway through or store a vehicle halfway through a job. This newest guy has masses of indoor space (his bread & butter is lorry repairs) so it was no sweat for him to just stop when he saw the cylinder, roll it into a corner, wait for me to come in and see it for myself, and talk it over. If you find a mechanic like this - transparent, no pressure, not rushing himself or you, lots of covered storage space - hang onto them. And inspect a car for yourself underneath before you buy it. And don't take a chance on an engine that rattles or knocks. If it sounds clapped out, it probably is.