Hi Andrea Taylor,
Please refer to the guidance here:
Goods that are in the UK at the point of sale
The online marketplace will declare the VAT on the sale to the end customer on their VAT return, this does not need to be declared on your return. However, as you would still be responsible for the import into the UK, you will have a deemed zero-rated sale of the goods imported into the UK to the marketplace which you will need to declare on your VAT return.
As zero-rated box 1 will be 0.00 and the net value will be declared in box 6.
Any import VAT you are reclaiming subject to normal input tax rules would be declared in box 4 and the net value of the import in box 7.
For guidance regarding VAT on services supplied to you please refer to notice 741a:
Place of supply of services (VAT Notice 741A)
In particular sections 6.3 and 6.4.
The supplier would need to determine whether UK VAT is due on their supply.
Where the place of supply is determined to be outside the UK then no UK VAT would be accountable on the supply as this is outside the scope of UK VAT.
Thank you.