Did the light go on? If the sensor isn't worn thru and triggering the light, then you can reuse them, as long as you don't break them when you try and pull it out of the old pad. There are only two sensors, one in the left front and one in the right rear. However, if the light triggered on mileage rather than the wear sensor, maybe you don't even need pads - did you check how worn they are?
Minidave thanks, the light is on and the pads are worn. Its just my first brake job on the Mini trying to keep it simple.
You can find a DIY for the front brakes at Front brake pad replacement (Gen2) - Library in the Motoring Alliance Library