Hocus pocus

B's Focus went into limp home mode on Thursday evening. It seems to have righted itself but I felt obliged to do something.
I thought the best path to take was to buy an OBD lead and software from ebay at the cost of half an hour's garage labour charge (because I don't trust garages very much). It appears that the fault was a P0224 - throttle/pedal position sensor/switch B circuit intermittent.
Things were much simpler when the ignition circuit was the electroniciest thing on a car and the most complicated fault would have been a throttle cable snapping.
But the question remains - what do I do now?