PQC,the longhaul success for EK from MAN,is because DXB is it' hub,i estimate 90% of passengers from manchester are transiting dubai,to pakistan,india,the far east and australia.manchester to dubai as a stand alone route would be a none starter,
BA operate about 8 shuttle flights a day to heathrow,it's hub,offering around 1200 seats,more than emirates 2 flights a day to DXB.
it's a simple numbers game.other than new york,i cannot envisage a longhaul route from manchester that would be profitable for BA.