Thanks everbody for all the replies.
@Martin: they had a lot of playmo when I was there. But it got even better: they displayed an entire roman legion in playmobil, thousands of soldiers, cavalery, even a bagagetrain with oxcarts and tents. To my regret I have only seen it in pictures on internet.
The fact that few museums have playmobil may also have to do with Playmobil's marketing strategy.
@Gis: I'm also from the Netherlands.

All my pocketmoney goes to marktplaats.
@Justindo: I'll post some pictures now and then. I have only one wargame planned, for next summer. I will most certainly take pics of that and post them on the net.
@Wolf Knight: I will start my D&D-adventure the regular way and only the endgame will be played out in playmo in my garden. (Wonder what the neighbours will think of that!!!

). By then the players will already know who's who and they will have developed likes and dislikes for their adversaries and onther NPC's. Only to find them all portrayed in Playmobil. They already hate the romans.
@Warrior of Toys: That's exactly what I am going to do: portray their caracters in playmo. Not easy. One of them is a birdman and another is a gnome. I won't post too much here about the plot, because the players might stumble on to my posts and read them before the battle takes place. The battle is planned for the summer of 2011. AND THEY DON'T KNOW MY ROOM IN THE ATTICK IS SLOWLY FILLING WITH PLAYMO. Boy, will the be surprised.
About my background: I used to study archeology, hence my interest in Romans and Egyptians. I used to build model airplanes and nowadays I restore antique telephones. So I obviously will do some customizing.