A link to some history of Kent mining, if there's any Oast houses seen in other parts of the episode then it's definitely Kent.........
Coal Mining in Kent
From THE AVENGERS: The Living Dead (December 1966) two static shots of The Duke of Benedict’s mine.
I'm assuming that this is a mine in Kent, but the closest match to the winding gear I can find is in Nottinghamshire.
There looks to be only one shaft, which should narrow the field.