when I lived in Belgium the rule on traffic circles was give way to the right, same as at any intersection, not as in the UK or US where once you are on the circle you keep moving. Better double-check for the current rule.
I can't speak for Belgium, but the priority rule in France was changed some time ago. Under their infamous
priorite a droite rule cars already on the circle/roundabout had to yield to those entering it. A few years back they started changing this, painting lines and putting Yield signs (
Cedez le passage) on each road so that priority is now given to traffic already on the circle.
Many European countries do still work to a priority-to-the-right rule though, unless signs say otherwise. It can be very disconcerting when you are driving along a wide boulevard and have to stop to let something out of a side alley on your right.
A yellow diamond with a white border indicates that the road you are traveling on has priority and you can keep going. The same sign with diagonal black bar crossed through indicates end of priority, and that you must once again yield right-of-way to anything approaching from your right.