Currently, there is no way to watch any further than season 3 in the Netherlands.
Actually, seasons 1 through 3 are not even available here, but they were uploaded to youtube by a channel named 'Cheese Wedgie'.
However, he stopped uploading 3 years ago and I've been looking for a place to watch season 4, 5 and 6 ever since.
The only chance I've found so far is ordering dvd boxes, which come at €15 per box, three boxes per season so a total of €135, shipping costs excluded.
Does anyone have any good advice for me?