Everybody with a motability car pays at least �40 - every single one.
Nobody gets it for nothing - not one single person.
Your mother is not entitled to DLA as she can get around - having arithritis is not enough.
People get their cars on mobility because they can't afford to buy one and they can't get finance to buy one on usual finance terms and they need a reliable car. That is the only reason - IT IS NOT FREE FOR ANYONE.
And nobody who is fiddling the system will tell a salesman they're at it - the salesman will have all the details to make reporting them easy.
If you are intererested you can get the facts about motability here:
http://www.motability.co.uk/main.cfm?Type=CHSW
"If you receive the Higher Rate Mobility Component of the Disability Living Allowance or the War Pensioners' Mobility Supplement, getting a new car is easier and more affordable than ever. Through Motability, you simply turn part or all of your allowance into the car of your choice"