After leaving the EU the British Government have the following choices relating to VAT:

Governments are not disposed to follow your predictions (or whatever you call them). They will do what they do and, as is being demonstrated, will do regardless of the rightness be it legal, moral, or even rational. Their only barrier is other politicians who may or may not be less reprehensible. Anyone who has favourites will always wish to paint them in a better light. But that light can be switched off by history, and so it will. I can wait.

Here's you caveat expressed by government sources - viz a Motorway electronic overhead sign:
 FREIGHT TO EU     
 PAPERWORK MAY
 CHANGE 1 NOV