Are you for real mate, if we all took the stance of who would use a company because of this particular situation then we'd all have stock cars, lol.
& not being funny but anyone who has a map knows the risks associated with using audi & what they do anyway, so its there responsibility to check audi dont do these things, not the tuners at all, legally you have no case whatsoever, fact not fiction is what the courts look at & as for sale of goods act, uh sorry mate but try reading it again, cause as far as the tuner is concerned they did the job you paid them to & in eyes of law aswell, your case would have no merit whatsoever
If you then goto audi & they feck it up how can that possibly be the tuners responsibility to put it back on at no cost if they had done it correctly in 1st place, get real, its like buying a eg. can of coke from tescos & then drinking it & taking back & saying can I have a new one FOC cause this ones empty, uh you drank it sir so hows that for us to replace it for you without a charge, not greatest analogy but it makes my point completely, please seriously think about it, if you were the tuner & you had me come to you & say put it back on FOC would you say sorry no we didnt remove it did we.