You can do it from BHX - and cheaper than Jet 2.
Taking random midweek dates in July 2012, a return flying BHX/MUC/PSA and returning FCO/BRU/BHX will cost £188.90. Flying from MAN on Jet 2, including online checkin and one checked piece of luggage will cost £197.24. You will also get free food and drink on the outbound (admittedly not on the SN flights on return).
Of course, you will also save the cost of getting to MAN.