Yes to the “slot keeper” feeder LHR-MAN but AFAIK it was a BAE146 feeder wet leased for the QF ops. Unsure of livery. But it appears unlikely it had QF colours. I still maintain that QF have not had a narrow body aircraft in LHR since the 707 days.
https://www.airliners.net/forum/viewtopic.php?t=267425
The LHR/MAN service was operated by a BA aircraft in BA livery (maybe a 737 but def not a 146) and was for the sole use of QF passengers arriving on QF for the onward journey into MAN. It wasn't a 'slot keeper'. It replaced the direct Australia to MAN service which was unprofitable due the the fare structures and necessary crew change.