British Airways carry all Qantas' connecting passengers,
MAN-LHR, MAN-CDG, MAN-FRA and MAN-FCO. It's much cheaper to use BA scheduled flights than flying a B747-400 half-empty on a 1 hour flight! Qantas' passenger numbers from MAN have fallen since direct flights were withdrawn, to the benefit of Singapore, Malaysian, Cathay Pacific and Emirates - but while ever BA is involved with Qantas I'm confident there will be no direct service from Manchester...The first change to happen when BA took a stake in Qantas was the end of Manchester flights.
Qantas' charter flights from LHR take in Barcelona every Saturday.
On Wednesdays and Fridays various cities are served on a rotating basis; Barcelona, Istanbu, Venice, Stockholm, Naples, hessalonika, Izmir, Athens and Larnaca.
There are also flights to Istanbul or Barcelona on selected Mondays, Tuesdays, Thursdays, Fridays and Sundays.
All flights are chartered and operated on behalf of Royal Carribbean cruises, whose passengers will pay the premium for Qantas services.
The flights probably don't make vast sums of money, but this will be preferable to a full day's parking at Heathrow, which is very expensive, and it also maximises aircraft and crew utilisation.