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?

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.