In reply to DaddyT:
I really feel for you, but you must tell your insurers, because if you don't, and you still go, you may not be insured. If you have an accident or claim for illness they could have grounds for refusing any claim on the grounds of non disclosure.
Against that if cancellation is included, I would have thought you have grounds to claim for return of costs you have incurred so far, and this may include the other person's losses too.
Good luck, that's tough shit....