I have gone from HRM DLA to standard PIP. The Post Office staff said that I need a special form from DWP, not the decision letter, and send that to DVLA with my V5 and payment. DWP said I don't need a special form from them but have to send V5, V10 and decision letter to DVLA.
I actually taxed my car for a year (it was only £30) so that it was legally on the road and will sort things out before it is due for renewal!
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