That’s interesting, Gadget. Since the heir to the estate was Reginald Prendergast, it looks likely that it is the right family, at least the family of the Reginal Prendergast who married Sylvia Mabel Kirkpatrick. We don’t know if he was the father of Reginald Vereker Prendergast.
I looked in the census for a Reginald Prendergast and the only other one that came up was this one...
1871 Class RG10 Piece 104 Folio 33 Page 14 Reginald Prendergast age 7 born Northamptonshire, older brothers born in Ireland and Scotland father Lenor Prendergast and Marion. 22 Grosvenor Garden.
1881 Class RG11 Piece 98 Folio 123 Page 22 Reginald Prendergast (transcribed as Pymold) age 17, scholar, born in Harleston, Northamptonshire. Son of Lennre and Marion Prendergast. Lennre is a Lieut Col MP late Royal Scots Greys active. 22 Grosvensor Gdns.
1891 ClassRG12 Piece 72 Folio 25 Page 3 Reginald Prendergast age 27 born in Northamptonshire, Harleston. He is a Manufacturer (Silver). Son of Lenox and Marion. Lenox is a Colonel late Royal Scots Greys. 22 Grosvenor Gardens.
1901 Class RG13 Piece 85 Folio 31 Page 6 Reginald Prendergast age 37 born in Warburton Northampton. He is living on his own means. Son of Colonel Prendergast and Marion. 22 Grovenor Gdns.
If you Google Lenox Prendergast you come up with the family history here
http://www.links.org/links-cgi/readged?/home/ben/camilla-genealogy/current+c-prendergast116+2-5-0-1-0If you click on Reginald in the list of descendants it says he is of the Isle of Wight, which sounds encouraging. BUT, how do we get from him to Reginald Vereker Prendergast who was born in 1891, way before Reginald married Sylvia Mabel. Did he have a first marriage, maybe in Burma, which didn’t show up in the English BMDs?
Edited to add, I just realised that's Reginald is pretty well accounted for in all of the censuses, which only leaves him the 10 year gaps in between to pop off to Burma, get married and father a couple of children. I'm thinking that this probably isn't the right man.