Well you were not a pax in G-APNA nor G-APNB.
My father left LGW on the 9th to Khartoum & Entebbe in 'NB. On the 12th flew Entebbe - Nairobi - Entebbe in 'NA and on the 14th Entebbe - LGW in 'NB.
At this time they also operated G-AOVE and G-ANCE as well as 'NCD and 'OVI.
He had pleurisy in the May/June of 64, so can't help. At the same time he was flying ATL.98, Viscount, DC-6 and first flight in VC.10 in the April of '64.
Other Britannia's flown that year and into early '65 were: G-AOVA, 'VJ, 'VP,
G-ASTF, G-ANCH and G-ATGD.
Hope you track down the info you are looking for.
POSTFADE - Lovely shots - if memory serves me right, the 'gear up' shot was quite a long way down 02 at Paya Lebar and they had probably been quite flat when the gear went up and then climbed? Very nostalgic!