Manx/BA used to advertise as direct flights to BRU & CDG but it was not unheard of them stopping off at SOU and vice versa.
I think on top of these they did also operate to SOU as a stand alone destination with a J41…..not that frequent but think it was 1-2 flights a week….most probably an attempt to make revenue on a “ferry” flight positioning the aircraft.
Fares showing £65 one way to/from SOU at the moment…..be interesting to see the passenger uptake on this route.