A carer can help the person choose a car and apply for the Motability scheme, but they cannot do this on behalf of the disabled person.
An appointee is responsible for collecting benefits for the disabled person and deciding how they are used. They may be required when the disabled person is under 16 years of age or unable to look after their own affairs.
The appointee is legally responsible for the lease agreement on behalf of the disabled person. The appointee should make sure the car is being used for the purpose intended and the disabled person has full access to it. Any monies outstanding for the lease agreement are the responsibility of the appointee.