I flew with 99 Sqn at Lyneham from 1959 - 1963. 99 was equipped with Britannias, but the military version C Mk253.
A couple of photos from my album showing the military passenger layout looking forward. Standard seat pitch was 38", but to cram in more PAX pitch would be reduced to 36" (compare that to todays 31" pitch in civil economy - if you're lucky!)
At the time RAF Transport Command standard routing to the Far East was Lyneham - El Adem - Aden (Khormaksar) - Gan - Changi and occasionally extended to Hong Kong.
Looking towards rear
..and in CasEvac layout.