Rescorla's the most famous. It's been somewhat of an issue tracking down actual Brits who served over there under the US flag, especially the KIAs. They aren't recognized in US records by any foreign citizen status.
Most Brits in Nam transferred into the AUS or NZ Army from the UK Forces. After the Malaysian Emergency wound down in '60 a few SAS Troopers transferred over to SASR once Vietnam started heating up. Other than Rescorla, Tom Abraham of Yorkshire was a dual US/Brit who was a PLT leader in 7th CAV and L/CPL Stuart Wood of Staffordshire(?), joined USMC while a legal US resident are known UK citizens who fought under the US Flag. Wood was KIA in '68, AFAIK Abraham is still alive and back in England. There's been rumors over the years that SAS Malaysia vets did train USSF and MACVSOG on the ground in SE Asia but that's never been proven. They DID train SF stateside as the war heated up.
Interestingly enough, there are more Irish citizens(
Republic of, not Northern) known to have fought in Vietnam than Brits. There are around 25 on record and about the same amount who fought for Australia. At least one KIA US Army nurse was also an Irish citizen.
Tom Abraham:
Attached FileStuart Wood:
Attached File