A brief update. It's been over half a year and it's just not happening. I worked out I could buy a roll of black and white 120 format film and get it developed (only) for about a tenner, including postage. So that should have meant I could "easily" do a roll a month; which isn't much for some people, but or me would have been a huge improvement over 2012.
But in all that time I've managed to shoot and develop zero rolls; ok, I have shot two rolls to this plan, but I've been unable to get them developed.
I can't do it any cheaper.
So I guess I'm just resigned to waiting.