Astounding photos - thanks S'land.
I'm not sure that it was a Sunderland; I am going on what my Mum always said (she's no longer with us to ask) and I assumed it was an RAF boat, because she was a Flight Officer WAAF at the time.
There is no mention of the type in the 71-page account of the journey from Liverpool to Cairo (the first part was by ship to Lagos), but it's a fascinating story of how how some 28 WAAF pioneers joined Middle East Command. There is mention of the BOAC office in Lagos though, so I think PPrune has come up trumps again. The C Class photos look exactly right...
Cheers, WW