I remember listening to a really creepy dramatised horror story on the BBC when I was a child (probably 1985 – 1995). It featured a couple driving through an eerie countryside who climb a tower (might have been a church tower), but on descending find that the stairs go on forever downwards. I think it ended with them trapped on this endless staircase. Possibly there was a clock on the top which struck at some point.
I thought it was part of the Man In Black / Fear On Four series, but having looked through all the episode descriptions, I haven't found it.