This is a long shot. There was a one-off horror drama shown (I think on BBC) sometime in the mid to late 1970s, at around Xmas time. It was set in the late 18th or early 19th century and was about a man who was convinced that the tree outside his bedroom window harboured a nest of large spider-like creatures with human baby heads. At night he was convinced they were watching him and that he could hear them crying like babies. Eventually a storm broke the window and the creatures ran in & attacked him; I remember a shot of him lying on the bedroom floor with these things sitting on his chest, sucking his blood. I definitely haven't imagined this one! Any clues out there?
I don't know about the BBC programme but this is very similar to M.R. James short story called 'The Ash Tree' - you should be able to get the full text from Google. Maybe your programme was based on this story?