Perhaps I can shed just a little bit of light about Kingsgate Davidson.
Their factory was in a disused chapel in Ivydale Road. London S.E.15 When they ceased trading in 1966 (I think) their tuning contracts were taken over by Rushworths, including two of Kingsgates tuners, myself, and Doug Littlewood.
They looked after many jobs in London and the home counties, and also had a regular quarterly tuning round in Wales.
As well as Mr Davidson Snr., there was also Douglas Davidson his son.
Ralph Arnold, one of the organ builders employed at Kingsgates, went out on his own when the firm ceased trading, and did some rather good work in Kent and surrounding areas untill about ten years ago.
Tom Robbins also from Kent, who used to work in the drawing office at H.Willis's, took over some of the tunings from Kingsgates when he started up on his own.
Sorry I can't give you any further information.