I had those stupid tri locks on one my car when I got it, the key snapped the first time I tried to undo one of the bolts. Took it down the local tyre place and they air chisled them all off in about five minutes and only charged me a tenner. Although I do all my own servicing and engine jobs, some jobs require specialist knowledge and tools, this was one such case, I would get on the phone to some tyre places and see what they can do.