Hey Scouseboy, I think it goes without saying that it was a large country house belonging to someone wealthy.

It's original purpose may have changed over the years but it would have started out as a house ...
Regarding the map. It may not be worth you printing it out. There are many Ordnance Survey maps online via the NLS. The side by side facility is very useful for comparing the 'then' and 'now'. I need to check coverage though ....

The trouble is with viewing plans is that we don't know the layout/plan of Caz's house. There may be more buildings behind for example which we can't see ... or as many suggest, this may since have been extended or substantially altered.
Presumably the "mansion" you are referring to is that Welsh nursing home?
