Hi Alice,
If you use google to do a keyword search for "OLL Fitzwilliams", you'll find some links to his academic papers in the Aeronautical Journal:
"Pursuit of the Aerial Carriage":
https://www.cambridge.org/core/journals/aeronautical-journal/article/pursuit-of-the-aerial-carriage/F8BE724E3589C6A4FAF9A395B37BB0E1"The Engineering Reliability of Shaft-Driven Helicopters":
https://www.cambridge.org/core/journals/aeronautical-journal/article/engineering-reliability-of-shaftdriven-helicopters/A83B119629952A6A862FF85C77678BEEAlso:
RE: the
American Helicopter Society https://vtol.org/files/dmfile/commentaryMJ141.pdf:
"The organization was international
from the beginning, as British rotary
wing experts were asked to join the
fledgling organization despite a virtual
wartime moratorium on rotary wing
development in the United Kingdom.
Early inductees included Royal Air Force
Wing Commander Reggie Brie and Air
Ministry leaders James A.J. Bennett,
O.L.L. Fitzwilliams and Raoul Hafner.
During the War, Brie was instrumental in
establishing a British purchase of 100
Sikorsky R-4s for the Royal Navy, while
Fitzwilliams helped establish the
licensing of Sikorsky helicopter designs
by Westland. Bennett was initially the
Chief Technical Officer for rotary-wing
aircraft at the Air Ministry, and then was
assigned to Sikorsky Aircraft"
There is a piece by O.L.L. Williams in David Gibbings' anthology, "A Quiet Country Town: a celebration of 100 years of Westland at Yeovil" (The History Press, 2015)
From Matthew R. Uttley's "Westland and the British Helicopter Industry, 1945-1960: Licensed Production versus Indigenous Innovation" (Routledge, 2014) - OLL Fitzwilliams was Designer on the W.6 at Weir in 1940, at CLE (Central Landing Establishment)/AFEE between 1942 and 1945; and did Rotachute work with Raoul Hafner.
1951 article in
The Straits Times:
https://eresources.nlb.gov.sg/newspapers/Digitised/Article/straitstimes19510705-1.2.142 Regarding Westland Aircraft Ltd., here is where you can find company records:
https://discovery.nationalarchives.gov.uk/details/c/F168040