Well, the entitlement to/ details of 'von' aside (thanks for the information, Netty!), for completeness's sake/ reference of anyone who might be interested:
The Frederick Hugh Sasse, Gurkha officer is presumably he- a Lieutenant in the 1/5 Royal Gurkha Rifles, Frontier Force- whose M.C. was announced in the Gazette of 23 August 1945; the only other Frederick Hugh Sasse for whom I could find a record was born 1924 at Lichfield, Staffordshire, mother's surname 'Herman', and died in 1987 at Kensington/ Chelsea. I would hazard a tentative guess that he is the same man referred to as 'a prominent Lloyd's underwriter' who, as part of a syndicate, apparently sued a Brazilian reinsurance company in 1978 (details of which can seemingly be found in many places online), but given the lack of details one avoids stating anything with certainty. Additionally, the name and location might indicate a relationship with the other F. H. Sasse who d. 1915; perhaps a nephew or such, in which case the name is still given only as 'Sasse' for Frederick Charles of Redcliffe Square, as above, regarding whom I can't find anything useful at present.
EDIT:
ethnicelebs.com/joshua-sasse - this source (the credentials of which I have no idea whatever, but the 'Herman/ Herrmann' detail augurs well) gives Lt F. H. Sasse's father as Cecil Duncan Sasse (b. 1892, a Lt-Col in the Australian Army it seems, who got a D.S.O.) and his mother as Zara Herrmann, Cecil being another son of Frederick Charles and Anna Sasse of Redcliffe Square (see above). Frederick Charles Sasse's father was apparently Frederick Richard Sasse, born in Belgium (apparently of the Foreign Office, and son of a Richard Sasse, as per the Gentleman's Magazine). How this factors into anything regarding the use of 'von'- if at all- I have no idea.
Just for future reference, should it ever become necessary.