While looking for something else I found this website
homepage.mac.com/philipdavis/home.html
which seems to be a list of all castles and fortifications in england and wales with map coordiantes . Potentially useful I think
Great find. Bookmarked. 
Yikes, thats a lot of data indeed!
Excellent find!
Happiness is a well-codified source of semi-obscure but very useful information.
GEE!! Happy noises!
What a great site! Thanks for the link!