Hello Fab01,
I really wouldn't worry yourself in regards to your English as from reading what you have written in your post above I believe you have a good grasp upon the English language. Indeed your post is written pretty well especially when it is compared to posts from myself and I should know better.
When it comes to live radio I would also like to say that some presenters do speak rather quickly. Even I have problems keeping up with some American Radio stations and I'm a native Englishman. Or rather Welshman.
As my first (and I am sorry to say only) language is English I do not have the insight into learning to fly by using a second or even third language. However I have spoken to many people at a school in America who said they had the same worry as yourself but wondered why they were initially worried as they had no problems at all.
They also said that by living and disciplining yourself to use the English language whilst training, you will considerably improve your understanding and command of the English language.
All the best.
Charlie Zulu.