I think there is an exemption for no tax if you are driving to a port to permanently export a vehicle. I’ll have to check it when my kids have stopped fighting and go to sleep but it does seem to ring some bells in my head full of nonsense. You would of course need proof you were exporting it , paperwork etc… and not just off to France for your holidays…
I’ve just checked, the exemption I was thinking of is only applicable if you’ve bought the vehicle specifically for export… so you’ll have to tax it, then ask for a refund