Natural, what you say about listening to this and that in English is the same as millions of people do in many non-English countries.
Yet these millions do not write in such clear English as you do.
Yes, but individuals are different, also within one country. How can I put it in a way it doesn't come out wrong, except to say I'm not the average Norwegian when it comes to understanding English (or average in most other matters, for that matter, hehe)
Also, in obverse to what you seem to say, most non-native English speakers tell me that they understand other non-native English speakers better than they do native English speakers.
And, I hope you do not speak with a Jersey accent!! 
What I meant was that I personally have seen with myself that I
speak (pronounciation) better English when I speak to native speaking English people as opposed to foreigners to the English language.
As to understanding English when someone speaks it, I find that relative. I find it extremely easy to understand someone talking in a clean Oxford accent or, say someone from New York or Texas like Alex Jones. Understanding someone talking native English from northern England or Scotland however, I find very difficult.
I don't actually know what kind of accent I myself speak English in. It is probably a mix between mainstream American and Oxford English, leaning heavier to the latter. Or so I'm told by native speaking persons when I have asked.