Alex,
I don't know the full ins and outs of the UK ATPL. This "expiry" thing seems to be a UK thing. I got my JAR ATPL last year. My Aus ATPL is valid indefinitely, just have a current medical.
It seems a bit harsh to have to do a full type rating again just because you haven't flown the type for +5 years. An abbreviated one would have been sufficient.
Pester the CAA. Have a really good look around the site. There is a lot of info there but sometimes not always easy to find. Surprised? No, didn't think so.
Jamup,
Not at this present time.