Hi Chris,
Unfortunately, I haven't seen this film.
Anyway, I found these YouTube clips:
According to the church scene clips, the church is definitely the
Church of St Mary the Virgin, Village Road,
Denham Village, Buckinghamshire, UB9 5BH.
You can compare the church scene clips with the 1st and the 2nd picture from this website:
nb Ten Bob Note
On the first clip (0:00 - 0:09) the scene including the church was filmed in Denham Village. But there are some changes now...
1. The small cottage on the right (where is the corner of Village Road leading to the church) was demolished (probably in the 1960s). I checked this on some old maps. On 1932-1938 map there is this small cottage. There is still also on 1960 map, but on 1970 map this small cottage is gone.
2. On the other hand, the cottage on the left is still there (called the Cedar Cottage), but it is altered. Now, there is an extension on the right side of the cottage.
Here is a Google Maps Street View link:
The church scenes from Kind Hearts and Coronets = Denham Village
Best regards,
Greg