Thanks people.

Unfortunately it looks like my various insurers won't cover it, each one of them has an exception this falls into.

I guess I didn't realise that despite it being a ticket to London bought via a British airline my European rights wouldn't cover me. MSE suggests in fact it's just untested in courts and in fact there is a chance it would be covered, but obviously the airlines will take a position favourable to them until proven wrong.

Exceptionally frustrating given how loyal I have been to BA.

Thanks

Becky