Given that nobody else reported the problem in question (that OP knows of), it's perhaps possible that either:
A: Tesco have received a small number of complaints and are keeping them seperate in the hope nothing comes of it
B: A small amount of fuel in the OPs "delivery" was contaminated (is this possible?)
C: The fuel was contaminated, but only enough to cause issues for certain cars (again, is this possible? Different grade of filters, pre-existing problem with injectors that was set off etc.?)
I know the garage the car is at and can't imagine they'd be lying to get some more cash in, especially given that it's been the same garage OP has used for years with this car.