From the Gov.uk website
“ VAT is charged on all goods (except for gifts worth £39 or less) sent from:
outside the UK to Great Britain
outside the UK and the EU to Northern Ireland
VAT is not charged on goods that are gifts worth £39 or less.” The only time you wouldn’t have to pay VAT would be if the seller had included it in the price and in this scenario they wouldn’t have. Not sure what would be the case with a book for example which is non-VAT in the UK but better to expect to be charged than surprised. And as an extra joy you have to pay the VAT on the value of the item, shipping & insurance and any duty you’ve had to pay
https://www.gov.uk/goods-sent-from-abroad/tax-and-duty