You'll need to go to Liverpool to get the Easyjet flight but this probably strikes the best balance in terms of cost/convenience (train from Manchester to Hunts Cross Station, bus 81a to the airport).
http://www.easyjet.co.uk/EN/Planning...ation/lpl.html
The trains can get crowded though so book your seats in advance:
http://www.thetrainline.co.uk