Thanks to all for the replies, I am reassured. Sorry for posting the message twice, it did not show up on my newsgroups uk.d-i-y list at all and I thought it had been 'lost'. Need another service provider I think, it needed a google search to turn up the lost post and the replies. I wonder how many replies to my questions I've missed in the past because my service provider was rubbish? ( Onetel ).
Andy.
PS: I figured the value was a rebuild cost, but I had this vague question in the back of my mind, what if they couldn't rebuild it in situ? What if a mineshaft opened up and it was too expense to cap? In that case, if you're given a wad of cash which is purely the rebuild value, you're out of pocket. An unlikely scenario I know but I'm a doom-monger at heart and like to pose awkward worse-scenario questions!