Lobster wrote:

My parents have recently been approached by their next-door neighbour
who wishes to buy a strip off the end of my parent's garden, presumably
with a view to gaining rear access to their property.

Thanks a lot for all the really helpful info!

My parents just *might* be interested in doing this. One of several
questions raised, though, is how would you put a valuation on this bit
of land? From memory, my guess is that the land would be of no
particular use to anybody else; ie not large enough to build a separate
property on.

Update on the above... it turns out that the area of land at issue is
somewhat larger than I'd thought. My parents have had a tame builder
take a look at it, and he says that it's definitely potential large
enough to be a building plot, and in a better economic climate could be
worth a pretty eye-watering sum if planning permission was forthcoming.
My parents certainly wouldn't want to build on it as long as they are
living in their current home, but it certainly means that the neighbour
is going to be told 'thanks but no thanks'!

David