Whether you decide to study in London, or in Berlin, English language is the most important factor which will determine if you are or not eligible for a study abroad program.
If you do not know German, you will still be eligible to study there, but the English language will be required.
There are different tests that you will be taking before getting the green light for studying abroad. TOEFL test, EST, or university entrance test which for international students will be on English. If you are a student and do not know the language of the country that you are going to study, than you should seriously find a way to learn either the language of that country or the English language (if you do not know it). But do not panic, because in most of the countries that allow study abroad programs, there are different courses for students. But in this little guide, I will try to be more specific on how to find a good language course abroad.