There’s an interesting article in The Times here. This should be free to read though you may have to sign up with an email.
The TLDR version is that tourists from abroad who buy a watch without UK VAT will have to send it directly to their home address, meaning they can’t sneakily wear it home in the hope of avoiding taxes in their own country. This could make it considerably less attractive for buyers from other territories to buy in the UK - according to the article, for a Chinese buyer it would mean the difference between paying £6k and £10k for a Rolex GMT. This could have a significant effect on everyone’s favourite topic, Rolex availability.