As someone else haas said, the larger/more powerful/more expensive car you want, the more you have to contribute yourself. Even on the cheapest vehicles on the mobility scheme, all your higher rate mobility allowance is taken away and goes towards the cost of the vehicle. The exceptions are mobility scooters (yes, they come under the scheme!!)
As for PIP, I'm sorry to say that it has NOT been rolled out across the country as you would think from reading the posts above. DLA remains in place for millions of people and will continue until this government gets the programme properly underway.
The other point that seems to have been missed here for those who are envious of the mobility allowance is accidents. If a mobility vehicle is damaged in an accident, the registered DLA claimant of that vehicle has to make a contribution to the repair cost even in a no-fault situation. For the purposes of assessing this cost, the vehicle is divided up into its individual panels and you pay per panel. Any overlap from a damaged panel onto a secon or third panel incurs a charge of twice or three times the cost of the first panel charge. Think about it - it's hardly cheap is it?
Finally at the end of the lease you have to return the car almost as pristine as when you leased it or you get charged. The mileage must also not exceeed the stipulated annual mileage allowed or you pay an additional charge for every mile over the figure.
Please don't get the idea that it's a perk. These restrictions can cause serious anxiety!