Some countries outwith the UK have strict rules on receiving mail by getting it wrong you can risk a long delay or even worse non delivery if theres no sender address printed!
Out of all the EU countries Germany seems to be the worse! Get just one small part wrong and you risk a long delay or even non delivery.
To help you if you vist royal mails UK website and follow the guide below
On the home page click the link "customer service"
On the next page click the link "sending mail abroad"
On the next page under the heading "using international services" click the link "preparing your mail"
You will now be able to view all the countries listed and the proper way to address your mail.
To save endless visits simply print the page and keep it handy I have a laminated copy beside my table which works well as I do a lot of international posting.
Hope this information helps you.