Forgot to say, I used the M6 toll on the way there and (by accident) on the way back. On the way there I was charged as class 4 (~£10) and I even pressed the assist button to check it was correct, the guy apologised and said it was automatic due to the height of the vehicle.
But on the way back class 2

It’s saving me money already
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It may be due to a slightly iffy calibration on the sensor or it may be that the 2 cm made all the difference. Anyone with a really lowered van paying class 4? (Mine has a poptop so is a good few cm higher in places too)