Welcome to Orchid Board. I grow on the windowsill mostly as well, although I have a couple of new orchids which I'm told can go outside in the summer here.
The main problem with windowsill growing is that you soon run out of space... well if you are anything like me you do anyway!
In Austria winters are way too cold as well, and dark! So i am growing some in a terrarium and the ones in the windowsill are getting some extra light as well. Though in compare to nice natural sunshine it is still dark even with 4 extra lights in the terrarium.
I'm not Dutch, but live in the Netherlands, in Wageningen. I spent 3 month in the Westland area a few years ago for an internship at a vegetable breeding company in De Lier. Nice region, but it's way way to crowded for me! I'm growing on windowsills as well, and have artificial lights too since the natural light is far from being enough at this time of year!
__________________ Camille
Completely orchid obsessed and loving every minute of it....