Obviously, this treatment of your property is appalling.
You might want to put something in the agreement with regard to premature failure of the engine being their responsibility if the conclusion is that it has been over revved when cold.
I think the fact that they are asking you to sign a confidentiality agreement, somewhat bizarre. They are obviously concerned that this is going to go further than what they don’t want you to do presumably is have the whole thing in the newspaper or refer it to Kia head office.
You need something outside the confidentiality agreement which confirms the contents of clause 1.1.7 and details what they are going to do and then says that they will do this subject to the confidentiality agreement.
At this stage, you might want to consider stopping communicating in email putting everything in writing on paper.
The other thing that you need to consider is whether you really want this work done at this garage.
Perhaps I’m being paranoid, but I trust that you have a copy of everything that is on the memory card!
Other than the above, there’s nothing wrong with the agreement itself.
Can I clarify anything for you?