MAN-NCL was operated for a time by Air Kilroe (Eastern Airways).
MAN-BHX - not a hope! Much quicker to drive there with the new toll road.
MAN-LTN - nobody does it as far as I know. BA do MAN-LHR & MAN-LGW, Jet2 do MAN-LGW and Eastern do MAN-STN. EZY did LPL-LTN for a while but they pulled it a few years ago. I would guess that if they couldn't make it pay then anybody else would struggle. MAN-LCY could be worth a look, depending on the timings it could prove a viable route.
MAN-CWL - Air Wales do CWL-LPL. Didn't Southwest do PLY-CWL-MAN for a while?
MAN is already pretty well served for GLA, LON, DUB, etc. Most other UK destinations are either too close to merit an airlink or too small to justify a point to point service, even with a small aircraft. If Virgin and Railtrack can sort out the West Coast Mainline then flying from MAN to LON may prove to be even less viable for travellers to the city.