On further investigation the hole from the chimney appears to be an access route from outside.
As the weather is so nice today I'll be in the garden for most of it, but I intend to do some more digging later.
Here is the link to the full discussion at Period Property
http://periodpropertyshop.co.uk/phpBB2/viewtopic.php?t=6606&postdays=0&postorder=asc&start=0