Thanks for all your help so far.

I think the "extraordinary circumstances" seems to be an interesting get out - and not very well defined. I wonder if anyone with access to this information (I think I have seen similar on here before) knows what the LX systems say as to why this flight was cancelled.

The letter from Swiss says "technical problem at short notice for safety reasons" which sounds difficult to argue with, but who knows what was actually the case!

If anyone can tell me more I might take it further, otherwise I guess it is not worth the fight - I only have a ground agent an MANs word that it was a damaged plane (hit by something I think) - and even that might be called extraordinary and stopped for safety reasons I guess - althoguh why that should stop passengers being compensated I have no idea!

All help welcome!