There are so many mansions in England that are used for filming. I for one also care that its not done via CGI. I envision a dark mansion whose extensive gardens have seen better days.
Ooo, that sounds intriguing.
Tudor Gothic could be an interesting style to go in for Collinwood, and two different examples that I came across would be these:
Muirhouse Mansion, which, with its turrets, gables and chimneys, is sort of a cross between Lyndhurst and Greystone:
And Knebworth House:
And with Knebworth House there's the added bonus of:
A fence/gate with spooky gargoyles.
Its own cemetery on the grounds.
And its own mausoleum, complete with spooky tree.