Suggestion:
Join the UK-Dedicated servers sometime (Read the rules before you do anything else
) and set yourself up on the TeamSpeak server. There are two servers that get most of the traffic these days and they have different levels of difficulty so you can find something you're looking for. The folks on there mostly speak English (although I hear all sorts of languages from time to time) so it'll be a good way to immerse yourself in the language. You will hear English as spoken by people with several different accents and ranging from native english speakers to very well spoken second or third language speakers as well.
Several members are German so that may help too if you get stuck.