Have to plug Tonder Festival in Denmark again - lots of British (and British emigrant) music, a little Danish on the side, great atmosphere, though very well organised. Almost a huge family gathering on the last weekend in August. One of the drawbacks is, you have to buy tickets to individual venues; there is no festival ticket.
Then there is Rudolstadt, Germany's biggest folk festival, which takes over the whole town centre for the weekend (7-9 July this year), including the old castle high above the town. Even if you don't care for all of the music (it's world music in its broadest sense), it's well worth a visit for the location and atmosphere alone, and you get a weekend ticket. Besides, most of the venues are open air.
However, I don't see any fundamental differences to the British festivals I've been to (not many). - Susanne