This is not entirely correct. On domestic arrivals at MAN, you are considered 'clean' and it is possible to double-back into the departure area unless you arrive at gate 141.

If you're not gate 141 and arrive on an airbridge (which would be normal), you are directed off the airbridge down the stairs to the ground floor and you would normally then turn left to exit into the baggage hall and on to landside. However, if you turn right and walk down towards gates 144-148, you will see some stairs on the lefthand side. These stairs will take you back up to the departure level and you can eventually get back into the main departure lounge (and up to the BAEC lounge). There used to be a sign saying 'transfer', although I can't remember whether it's still there.

If you arrive at gate 141, you have a problem, as the ground staff generally direct you because you cross the incoming passenger corridor into the lounge and so they corden off all routes except the staircase that takes you directly into the baggage hall with no possibility of using the above rooute (since gate 141 is in a different part of the terminal). It might be worth asking to go into the departure lounge if you say you have a connecting flight, but I sense they may not be up for this.