From this site:
British Cinema Greats | the best British Movies, Films and Cinema on the net.
Sir Ralph Richardson - Lt Cdr (FAA)
Sid James - Lt (South African Army)
Sir Richard Burton - (RAF)
Sir Richard Todd - (Army)took part in D-Day attack on Pegasus Bridge (as well as on film!)
David Niven - Lt Col (Army)
Peter Ustinov - Pte (Army)
Peter Sellers - (RAF) where he met Spike Milligan, Michael Bentine and Harry Secombe
Nigel Patrick - Lt Col (Army)
Sir Laurence Olivier - Lt (FAA)
Kenneth Moore - Lt (RN)
David Niven - 2nd Lt (Army - HLI)
Christopher Lee - Flt Lt (RAF)
Jack Hawkins - Capt (Army - RWF)
Donald Pleasance - Flt Lt (RAF) Prisoner of War
Desmond Llewelyn - 2nd Lt (Army - RWF) Prisoner of War
Denholm Elliot - (RAF) Prisoner of War
Sir Anthony Quayle - (Army - RA) operated as a spy in Albania
Sir Alex Guinness - (RN)