Thanks for the advice folks.
Hee hee!! All I wanted was to stop the moisture spoiling the finish. :p
By the way, talking of finishes. I've just been reading a book called "Understanding Wood Finishing - How to select and Apply the Right Finish." (American Woodworker/Readers Digest)
In my humble opinion a book on a par with the Neil's polisher's handbook. Not so much detail on how to do it but loads of background info on why do certain things and chose certain finishes. Debunks quite a few myths too