This is a very dark grey area. If an item is failed as “dangerous” and you had a problem whilst driving it away from the station for repairs (which you’re fully entitled to do) your insurance would likely be inoperative.
You could get it removed by recovery firm, ££££, so garages try to use this as a bully tactic to encourage you to leave the vehicle with them. Some do, the more savvy ones dont. Since this came in, I personally haven’t heard of 1 case of someone driving a vehicle away where the “dangerous” item caused an accident on the way home, though that isn’t to say it might not.
As I said, a very grey area. Your risk, your decision!
Tony.