Payments will start to come to Motability Operations shortly after your agreement begins. Your benefits agency will be automatically notified that a new agreement has started after you have taken delivery.
Also the free road tax allowance it goes onto the Mb car as well.. So they need that as well to place your order so i doubt you’ll get a payment on the 22nd but you could.
As for pip mostly it’s in arrears, dla could of been both upto 1 week in advance 3 weeks in arrears, it depends and i guess if you was swapped from dla to pip it would be the same and at what point you actually made the claim in the month.