Hi,
If the goods are over £135 then company B, being the importer of record will account for the import VAT. When the goods are sold then this will be a sale between company B and the end customer and so UK VAT will need to be charged.
For goods below £135 then the sale between company A and company B will be accounted for under the reverse charge procedure. You can see guidance here:
Goods that are outside the UK at the point of sale
Please see section 'Business to business sales to UK VAT-registered customers' in the link above.
There will then be a supply between company A and the end customer and VAT will need to be charged on this.
Thank you.