I never had much problems with roundabouts when I first moved to England: road design is such that it naturally pushes you towards taking it in the right direction.
The one thing to be careful, as somebody mentioned earlier, is early morning or late evening (viz. when you are not yet 100% fully with it or when your concentration starts to wane) when one can all too easily turn onto the right hand lane, especially on country road. You can practice as much as you want on a parking lot. This won't help with this.