Two years old Simon?? You bought the boat in Jan 2008 didn't you? My last insurance had a 2 year survey stipulation; and it was "to the day", and luckily I was able to send in the survey 2 days before it "expired". So if your survey was in Dec 07 it -should- still be valid until the end of the year (but of course that would depend on the insurance underwriter).
What is "sea-worthy" condition? That sounds like a huge loophole; as if the boat sinks it is obviously not "sea-worthy" at the time of the sinking. I would definitely ask for clarification and a definition of the term.
When are you coming back to US to buy another boat? It's a buyer's market here now!!