Location from 'Unnatural Causes'

Could some expert please help me find out the name of the church in the scene where Dalgliesh enters the church at 0:29 (Unnatural Causes)? It has wooden angels attached to the ceiling and a very narrow staircase next to the entrance door leading up to a small room. I always wondered what this room was intended for?
I've been to this church (Walberswick or Blythburgh???) in 1995, but forgot where it was exactly. It's connected by a walking trail to two other old churches.
All I remember is that it was in East Anglia not too far from Aldeburgh and Southwold.
waldenpond 88 at hotmail dot com
Thanks!

I also would be delighted to find out more about the other locations, for instance the beach where the boat with the corpse is found.