Troublesome Tow Bar

My car was in the garage today for its 20k service. I had arranged for a tow bar to be fitted at the same time. The Toyota Rav is incapable of having a rear-mounted bike rack fitted so I had to resort to having a tow bar fitted so we can use a tow bar mounted rack. The car was due to be finished by 4:30pm and I duly arrived at 4:40pm. The car wasn't ready and they were struggling with the electrics for the 7-pin adapter. At 5:30pm they admitted defeat and put the car back together in a working state and insisted on cleaning it. I left the garage at 6pm. They were terribly apologetic. It seems that when they connected the wiring for the 7-pin adapter the car indicators flashed at twice the normal speed. Once the new wiring was disconnected everything worked as expected. They have placed an order for a new wiring kit as they believe the original to be faulty. The car needs another visit to the garage when the replacement kit arrives. The issue is the inconvenience of a 50 mile round trip to drop the car off and the same again to pick it up.