I think the original flight enquired about was in 1969, and from my notes the long haul passenger-capable Britannia fleet at that time seems to be :
RAF - 22
Monarch - 7
Caledonian - 5
There were also several cargo operators of the type as well that year.
Jonesy, if you can ask your mum .... to help, the RAF ones were grey, the Caledonian livery was dark blue, and Monarch were yellow. The RAF aircraft would certainly have had seats rearward-facing (a fact that many remember), the civilian operators could have had them either way, depending on how long the aircraft was to be in RAF charter service, they used to turn them round for longer contracts.