Wheel Nut:
I would suggest the calibration date is fixed with no grace, however if the vehicle is booked in that should help. A commercial MOT does not have to be on the actual anniversary as long as it is done before the end of the month it’s due.
i alway found that last part to be a interesting loophole. i always booked my lorry in for the first of the month AFTER it was due, so i gained a extra month every time i mot’d it. 