Scam - I am in Germany and never got anything from the Finanzamt. Even if you sell to buyers in Germany, you are not reponsible for any taxes in Germany - as a UK citizen, you pay your taxes on your income in the UK and nowhere else. And as an Amazon affiliate you shouldn't worry about foreign customers at all. As a seller (of own good) I am not 100% sure, but usually nothing to worry about.
To check if this is a scam mail, copy some text of it into the search field of your favourite search engine. Quite often you find some results discussing this same mail.
[edited by: lorax at 3:12 am (utc) on Jun 11, 2013]