It depends if the item is taxable in the UK. For example if you are buying say a soft drink, that is subject to VAT here, you will pay VAT on entry to the UK. You will then be issued a C79 (i think) by HMRC so you can claim this back. The other aspect is duty and for this, you need a commodity code from your supplier. When you have this you can go onto the gov uk website and search the import tariff from China which will tell you the amount of import duty that is payable on the items you have brought in. Obviously you dont get this back and will need to price your items for sale accordingly