You're right (about Yarmouth). I had forgotten. It was quite well thought-of among organs in that part of the world.
Davies's electronics were developed from a one-off electrone built by Maurice Grant long before the days of GD&B. The actual prototype was bought by Maurice Maxfield of Waltham Cross (I remember him from Organ Club meetings many years ago).
I once played the Davies hybrid organ in St. Peter's, Sandwich, Kent. The Great had pipes but the rest was electronic. I was 14 at the time, which makes it 45 years ago and I don't remember much about it!