c. 1980, Mistral Films, near hardcore loop.
This stars Brigitte Lahaie and Richard Lemieuvre; so the other girl may be French rather than British, though the document Brigitte signs is in English.
Richard Lemieuvre types out a document giving himself a pay rise and takes it through to the boss for her signature. On the way in he fondles her secretary (NK0616). She listens via the intercom as he earns his pay rise with the boss, Brigitte Lahaie, across the desk. Then the secretary comes into the room and is made to join in. Finally, with Richard sprawled across the desk in exhaustion, Brigitte takes the document, ups the amount from £5 to £10 and signs it.
This was shot with very graphic close-ups of cunnilingus and brief finger penetration, but no sight of penetration by a penis.