My experience is most companies are not interested in selling cross-border. Of those who are interested, postage will be 1€ to anywhere in France, but 1m over the border into Spain will cost 34€.
As for Language; Paypal Spain will not speak to me in Engligh (even though the whole site is already designed in English!), and will not let me register because my bank account is in the UK. Paypal UK will speak to me in Ensligh, but not let me put my correct address, because it is in Spain. Trying to speak to them, it is really the same company, and is based in Switzerland to get around all the annoying Euro laws... (The English / Spanish thing is just made up to make things harder for people)
Amazon and ebay are OK, but you don't find out that the marketplace seller doesn't ship to Spain until you actually try to order; it is not possible to search for only things delivered to your country.
As for rights, trading standards are not interested because I don't live in their patch, and the equivalent in Spain, the local police are not interested because outside Spain is outside their juristicion (no I can't spell),
I'd rant more, but it's after a 3-course lunch & cerveza, so I'm relatively relaxed.