I had a very similar problem with my Rover 25, thankfully before Rover went bust. The car started jumping, surging and then lost power so it would only rev very low, and the engine computer light on the dashboard came on. The handbook said "don't drive" so I called the AA who found they couldn't attatch their computer as Rover had modified the plug. They wanted to tow me to a Rover dealer, but on starting the engine it was ok, for a while. Then the same happened again. My Rover dealer couldn't look at it for 5 days and said there would be no problem with short journeys.
Once they plugged the car into Rover's computer diagnostics, they said it was the oxygen sensor, replaced it free of charge, and the car was fine.
I had never heard of an oxygen sensor, but it was all in the news over the past few weeks with the dodgy petrol fiasco.
Presume you didn't fill up at Tesco/Morrisons/Asda over the past few weeks ?
I would certainly demand to know what Ford's diagnostic computer is saying before you splash out. Are modern engines any better for all this computerised stuff under the bonnet. There was a time I could lift the bonnet and know what everything was and how to replace it !