I had the very same problem about 1 year ago. The tiles were bowed, there were three different size tiles in the batch , some were 597, some were 600, and some were 610!! The tiles scratched when grouted. All of it came from B&Q. I didn't get paid, (A weeks work 50m2) . B&Q said it was my fault i used the grout that they had supplied!! And they said i should've checked that they were all the same batch .
I did!
They were ! (at least according to the boxes)
I saved some leftover tiles to show them.
They pretty much told me to fornicate off and sue them!!
I can feel the anger bubbling again now.
Truly the worst company in the world.
You should have refused to fit the tiles if you realised the calibration was so far out, and got the customer to take them back to B&Q, and let them sort the issue out.