Buying tiles in the EU and take it into the UK for "personal use"

I have been refitting my house in the UK. The tiles I need are almost unavailable in the country, and where I could buy them, they were more than twice as much as in the EU. These tiles are made in Poland. I would buy and take them. I can see there is a 630 GBP limit for the online simplified rate. BUT is this netto or brutto? Because the final price is around 600 + VAT. The netto price is below the limit, the brutto price is over the limit. In which country do I have to pay the VAT?

The value is based on the actual amount you pay for the goods. If local taxes are added this forms part of the value of the goods imported. Please also bear in mind if you pay in local currency HMRC use their own exchange rates. It may be that the retailer of the tiles will operate an export tax refund scheme in which case local taxes will not form part of the value of the goods being imported. The flat rate applies up to £630 and the simplified rate above £630 . You can make an on line declaration in advance of travelling back. As each country operates its own tax regimes, Uk taxes/ VAT will still be due even if you pay taxes in another country.

Hi,
Import VAT is calculated on the total value of the goods you’re declaring plus any customs/excise duty due and is charged at the current UK VAT rate.
You may need to check with EU customs or the seller to see if they need to charge you sales VAT since goods are being exported to UK.
Please see below link for more guidance:
Simplified rates for bringing personal goods into the UK
Thank you.