My car has recently gone in for its MOT. It failed but I have a friend who is doing a Mechanic apprenticeship, he offered to do the repairs for me at his garage for cheap, however the money has gone directly to him and not through the garage. All the repairs went smoothly but after I took the car, his boss asked him to charge me £75 equipment costs. This was not previously mentioned or put down in writing, he also had no involvement with the repairs. Is this legal and do I have to legally pay this?