Last week I contacted Sky-Fun at Dahlemer-Binz about jumping in Germany, this was the reply:
Thank you for your request. You're welcome to come to us for jumping. The charge reads as follows: Height 4,000 meters € 28, - per jump. Simply come and bring your license. Sincerely yours
No guarantee that Stadtlohn will be the same, but it's a start.
As it happens I'll be in the Netherlands next weekend, and I was hoping to jump near Heerlen and the best options should be Schaffen, but they had strange insurance concerns last time I tried, so I ended up jumping at Spa instead.
Your best plan is always to contact the DZ in advance and try to find out what the local issues are.