I have finished this but not sure whether I am correct with 19 down as I don't actually get the parsing - Aged welder, say, shows craft needing gas AE?OBOT for which I have AEROBOT - can anyone put me straight?
Actually I've been out in the garden (though not in the pond 8))...yes, it's one of those where you need Chambers to provide complete reassurance - AE (aged) + ROBOT ('welder, say' - C: 'a machine, now esp computer-controlled, able to perform complex physical tasks, eg welding') = AEROBOT ('craft needing gas' - C: 'an unmanned gas-filled craft used to conduct experiments in planetary atmospheres'). It's sound, but rather dull...