Hi Bagso
As far as I know BCN, VIE, and DUB (not to mention BHX !!) are so far all in the same boat as MAN when it comes to possible direct China flights - occasional rumours (mainly on here), but nothing concrete on the table yet.
MUC is logical, it's a major hub for Air China's Star Alliance buddy LH, so they are probably looking at the availability of onward feed from MUC (including ironically to MAN via LH or SQ connections). MUC is also a lot less congested than FRA.
I doubt possible competition from BA is a concern for the Chinese - BA simply don't do longhaul from anywhere other than LHR/LGW. Apparently it doesn't suit their business model and the Chinese will know that.
No I suspect MAN just isn't far enough up the Chinese carriers' priority list just yet. Perhaps their LHR flights are not yet full enough or profitable enough to justify another UK point - they already tried and failed at LGW. Or the MEB3 are seen as being too strong ? Or UK visa restrictions are putting them off, APD, or any of the other possible reasons which have been put forward on here.
Personally I still think MAN is more likely to see the return of a HKG flight before anything to mainland China, based on the O&D numbers which have been posted by others. Whether either ever materializes is anyones guess at the moment.