Thank you for the email and the many leads you have been providing via your regular posts. I know they are appreciated by the regular readers of GenWeb even if you do not get responses. You certainly have been rather busy.
The Richard Garnet (RG) you noted in point (2) certainly strikes a bell and is very probably the RG I am trying to get birth details of. I have a copy of his wedding invitation (1912) given to me by my father. I think he died around 1956.
Grysil Davidson is RG's sister; whilst I do not have her birth detail, I know she married a Roy Gomes and they have two children; Maureen+Clinton Malleappah and, Dunstan+Ruth Leonard.