Put it in reverse and ease the clutch up until the car lifts up at the back, then do the same in forward(gently)do this a couple of times(gently)and you may hear a bang!it's free.It could be frozen on in this weather,quite common,if it doesn't work you will have to get underneath and bash the backplate with a hammer(handbrake lever off ofcourse)and you will hear a ping!it's free,then let the garage grease everything up for you.
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