Jeza is your car parked in the street or on your drive, if its not on the street them don't leave your blue badge in the car. In the London area before you can use your blue badge for congestion exemption you first have to register the badge + car reg with the congestion authorities, fill in the form with all the details of the badge holder etc. I fyou the badge holder will be in someone else's car you have to notify them 24 hours before you travel. This man is just trying to scare you and drum up some business.