I noticed that there are still some missing locations from some episodes such as Carpathian Eagle, which is one of my favourites, and I have managed to nail the location of Mrs Henska's house. The area has changed quite a bit since filming of the episode in the summer of 1980 but, fortunately, the church like building is still there and is now part of The Chiltern Hospital on London Road, Great Missenden, Buckinghamshire, which I believe is a private hospital. It's hidden away so was difficult to spot and it took me a few weeks to find.
I'll send you an email with some more details and a modern photo I found online as proof.
A fascinating site this is and I look forward to reading the threads and posts on here.
In the uk I’m so going to that hospital!!