Phil, if I were in that situation I would get an independent automotive engineer with appropriate qualifications to do a full report on the car, and then demand that Arun repair the faults identified, making it clear that I would then be returning the car to the same engineer for confirmation that all is now in order. Your Jag specialist may or may not be appropriately qualified.
The sort of report that I am thinking about is the kind that would be produced as evidence if the matter ended up in court, and the engineer was called as your Expert Witness.
You would probably have to pay for the reports yourself, so this is only worth doing if the faults involve a four figure sum, but it does mean that Arun know that they are going to have to satisfy an expert, so have to do the work properly.