Hi,
Your UK taxable turnover is made up of the supplies which you make in the UK. If the value of the imports are over £135 and you are not the importer of record then normally the consumer would become responsible for paying any import VAT applicable. As you are not the importer then you do not own the goods in the UK and so you would not be making a taxable supply in the UK.
For goods below a value of £135 then there will be a supply made to you by the seller and then a supply made by you to the end consumer. If you are not VAT registered then we would expect the supplier to charge you VAT on these goods. Your supply to the end user would then be a UK supply and this will count towards your taxable turnover. You can see the information below relating to this:
Changes to VAT treatment of overseas goods sold to customers from 1 January 2021
Thank you.