If when your car fails it MOT, it has days left on the current certificate, you can drive where/when ever you like, upto the date on the current certificate. If when your car failed its MOT, there is no current valid certificate, then you can only drive to where the car is BOOKED IN to have REPAIRS. If you drive from your house to the shops on the way to where your car is booked in, and the police stop you outside the shop, they are with in reason to report you.