Thanks for all the advice and feedback guys, and thanks for that gif above. very useful.
Well, i have had a few lessons since this thread and i feel my positioning and decisions have been a lot better then before. I have found that basically, just take your time when approaching roundabouts, approach it slowly and calmly and have a good luck to the right, if there's enough time to go then it's good to go. Just concentrate to the right, as you have the right of way to the cars of the left.
As i keep driving im sure i will even get better at it and a few months/years down the line, i'll be looking back laughing on how difficult i found big roundabouts! :P