Garage in Dublin 15 - awful service!

I left my car into a garage in Blanchardstown,.....I bought it there in September, and 6 weeks later it failed the NCT with several fails in the braking system. Admittedly its a used car, 2008, but I thought they were a reputable garage.......
Sooooo they worked on the car/handbrake but unfortunately sent me home in a car with a handbrake that wouldn't hold on a downhill, only uphill. Turns out they had put it back together incorrectly, and when my partner pointed it out to them they argued with him, and over the next few days gave us several different versions of what had happened and why the handbrake wasn't working. I was told the spring broke, the cable broke (even though it worked uphill), they had fixed the handbrake, they hadn't looked at the handbrake, etc etc the latest claim from them is that it was working when I took the car home.........and to top it off, they wouldn't tell me the name of the mechanic that worked on it, he was probably rushing out to the pub for Christmas drinks!
The car has since been fixed, and passed the NCT, but the radio is not working, and they are refusing to fix it, its a minor thing but in addition to everything above, surely they are foolish not to fix it, rather than have me and others bad mouth them ?