We have the UK distribution rights, which when it comes to Amazon/Ebay means fluffall as anyone in the EU is allowed to sell anything unless it's a regulated product (these are medical devices, but not restricted to OTC). On Ebay it was just as simple as putting "UK Seller" in the title and it's obvious our product will get to the buyer in 2-3 days instead of the advertised 2-3 weeks the eastern European ones offer so we still get the majority of the sales. With Amazon and the "win the buy box" you HAVE to be within 2% of the sale price to be considered for the buy box and they don't advertise that other sellers might be quicker at posting even if it's just 80p more.
Our recent scrap with Amazon is with a product produced by a Dutch company, manufactured in the West Indies (source of ingredient) and popular also in the USA. When I tried to add the products to the UK I was told the EAN's (barcodes) were already assigned to Amazon ASIN's (their unique identifier) and I had to use the ASIN, but the ASIN's assigned had not been used in the UK before so I had to create new products. Eventually I got them created but now I'm left with 2 products which have USA titles and are not descriptive at all to what the products are, and one in German and Amazon are reluctant to change them for the UK market even though our other international products have different names per region.
I'm still trying to get Amazon shipping cancelled when the sales adviser said on our current sales we'd be ideal for their system (4-5 orders a day currently on Amazon, our smallest sales channel) but when the paperwork came through a week later they wanted 20-50 through Amazon as a minimum and now we're having difficulty getting them to stop the service.