Hi again Tamjk - once again, you may already be aware;
Also from The London Gazette: 12th Jun 1965 - Queen's Commendation for valuable service in the air - Captain Donal Francis O'SULLIVAN, Senior Captain, British Overseas Airways Corporation
From 'The Log' (Official Journal of BALPA) Vol 20: "Vice-Chairman... Captain D. F. O'Sullivan, DFC"
And from 'Aircraft Engineering' (1965) Vol. 37 (10): (Page?) 330: "On September 15, 1965, Minister of Aviation Mr Roy Jenkins presented three Queen's Commendations and five British Empire Medals on behalf of the Queen. The Queen's Commendation recipients were T. R. Pigden (BEA), D. F. O'Sullivan (BOAC), and S. P. Jenkins (Royal Aircraft Establishment), while recipients of the British Empire Medals included L. J. Ralls."
Which together, seem to indicate that your BOAC senior captain, Vice-chair of BALPA and DFC recipient with RAF Service No 177841 are one and the same; and named Donal (rather than Donald, as per the - seemingly erroneous - Gazette entry for the DFC in 1945).
From your other research, do you have any more crumbs to feed the search - perhaps any details of the events leading to the awards of the DFC or QCVS ?