Originally Posted by
volar
I imagine BA charges the same for a given product regardless of the differing rules and rates applicable of the departure country and settle it up themselves behind the scenes. If BA are paying any tax instead of you, you won't get a VAT receipt.
Hence similar to duty free shops. Customer pays the same price irrespectively of whether he flies domestically, to the EU, or internationally. It's the duty free shop that will be able to claw back tax on products sold to passengers flying to non-EU destinations.