As far as I know BA have Airbus A319 (BA Mainline), various regional types (ERJ145 etc) of BACE and various CRJ/Boeing equipment of Maersk Air based at BHX, but no A320's. It's probably an A319 diverted into MAN. I remember when BA used to have A319's in their hangar at MAN from LHR/BHX for maintenance or whatever, they used to operate BA's Manchester services for a few days after their maintenance, MAN-CDG/MAN-AMS returns for example, in place of the B735's before returning to their bases down south.
Is the BA hangar totally closed now then? Did BA ever perform work for other airlines in the MAN hangar?
Cheers
Landing_24R