I am pretty sure these prices do not include VAT (because they are not registered with HMRC) and customs duty will also be payable since the brands they are selling do not originate in the EU, so chances are you will pay the same as Uk prices. Keep in mind you are viewing their "UK" site pages and the website is only a shop window for products made all over the world
. For EU customers they have to include VAT at point of sale and import duty to the EU will already have been paid so there would be no customs duty. If the products they sell mainly comprise goods manufactured in the EU they would be covered by the EU/UK trade agreement and no import duty would apply. They may still not charge VAT at point of sale however, and that then has to be paid by you.
Some EU vendors who do good business with UK customers, like Bikester, have it sorted. Their prices include VAT and I have always paid only their advertised price plus shipping for everything I have bought from them. Similarly if you buy from Ebay ( even the same sellers Ebay listings) VAT would be included and no duties payable.....and the price would reflect that).
My advice...look elsewhere!