In Enggland most churches have halls as well as churches. Tell 'em you're a third generation atheist, and you'd like to rent a hall for the night and they'd probably fall over themselves to give you a good rate, I reckon.

Schools or Community Centres might be the other option, they likely would be in England, but I've no idea how things like that work in the Netherlands. There might be laws against it or something.

Youth hostels in my experience tend to have rules about the time people come back at night. That would neeed to be checked. Otherwise it sounds a good option.