Who has made the Sales

I have the following scenario and am wondering whether someone could comment.

Company A is a UK based online business delivering legitimate products globally but the nature of products would be frowned upon by most banks so Merchant Account is a problem.  Company B is based in another EC country unrelated to Company A.

Company A would take orders on their site from consumers all over the world but check out would be via Company B's as if all orders are via Company B.  Company A would make the deliveries once payments are confirmed by Company B.  Are sales made by Company A or Company B, particularly that it is Company B's site eventually accept orders and payments?  If all sales are made by Company B which is an EC company, does Company A still need to account for VAT if goods are delivered to the UK and EC consumers?

Any comments would be appreciated.

Eddie