In reply to Parrys_apprentice:
As others have said it's perfectly possible to climb with two different sized axes* but it's not ideal. People take two mountaineering/walking axes when they're concerned about weight (i.e. high altitude stuff), I don't see any other reason why someone would buy a mountaineering axe hammer. You can't change the picks and they don't suit climbing well. You'd be better with a technical tool, keep your eye on ebay for some late season bargains and you'll probably pick up a pair of technical tools quite cheap.
* and B1/C1 boots PPP, I remember doing tower ridge with a 50cm cirque, 60cm grivel munro, some bendy walking boots and C1 crampons - stiff boots climb easier but bendy boots are what all the classic routes were put up in and there's nothing to stop you from doing the same on easy ground.