I have always gone to Nationwide autocentre for my car sevice, and last year they told me to replace the break disc/pad etc, and the whole thing costed about £400. I felt it very spongy/slippery when I try to break specially at high speed on M25, and I phoned them to say that it definately wasn't right, and I booked the car in, they took for a test drive and came back saying nothing wrong, just need some "ajustment", and told me to get use to the new break. I was scared to drive the car, so I paid others to take me to work in a car sharing scheme. I took the car to a different garage to service this year since I wasn't happy about the break work, and I was shocked to know that it was LHM fluid in my break oil tank, and it is completely wrong oil. I didn't even tell them about the problem with my break, and they said that was why. I called the Nationwide autocentre, spoke to their regional manager, and they said that the engineer did my car has left, and it was unlikely they have put LHM oil in there since it is rarely used in workshop and is only kept by the litre clearly marked LHM and it is green color. they offered me to reimburse my brake fluid flush (about 50quids I think), or a free MOT next year in their garage. I am angry that they wouldn't admit their mistake, the car has never been touched by anyone else, and I know nothing about cars. they are the people I have trusted with my life, and they have put me and others in danger. But what should I do now? is it worth to take legal action against them? Please help and advice me.