It very nearly went overboard but my recycling-conscience just stopped me!
Arne, thanks for your suggestions and while I nearly always fix things and make them last (The Westerly22 is 56 years old and our other boat was built in 1880!), not in this case. It's a faulty, dangerous product and should probably have a full product recall.
I think Compass just got it wrong and ended up with a copy that looks like the Origo3000 but the subtle differences are catastrophic. The tanks are not as high and the springs are not as strong and the "tin-can" seal is not as well executed and the fibre and mesh have too much space above them and the plastic knobs are cheap rubbish and the welding is atrocious.
Rest assured we normally have fire-blankets and extinguishers near the Origo3000 in our van and in the boat. In this case we were lucky there was an old extinguisher aboard for this pre-season picnic!
No reply from Compass for two days now. I'll email a different address tomorrow.
Pictures:
7mm clearance on Compass24 tank which is about 45mm deep.
1mm clearance on Origo tank which is about 51mm deep.
Tin-can can rim of Origo which is tight and might even have a black sealant inside.
Much rounder rolled rim of Compass tank.
Compass tank held vertically, dripping ethanol.