There may not have been black archdeacons in the Church of England during the 1950s but, at least, the village of Grantchester really exists and, whilst we were down south visiting my folks the other week, we went to have a look at. It is not far from the campsite we were staying on in Cambridgeshire.
The only scenes they film in Grantchester itself are those set in (and just outside) the parish church.
I actually have a link to the series, albeit rather tenuous. I baptised one of Robson Green's nephews. Pretty much all of his extended family were at the Christening but not the man himself, which was a shame as it would have made for a far more interesting anecdote.
Here are some snaps I took whilst treading where the reasonably famous had trod.