@Steve Evans, Yep 27!!
German's are very organized as well.
The rate you pay is layed out each year in the "duesseldorfer-tabelle"
It's a sliding scale based or your net pay. Remember the Germans have higher income tax (40-50%) but the cost of living is less. So when they see your UK 'take home' placed over the "duesseldorfer-tabelle" they get all excited.
To add to this a child get's a family allowance, which is split 50/50 to mother and father. If you are a German father this amount (kindergeld) is taken off the amount due for maintenance. BUT if you are NOT a German father, you don't get the 50% of the kindergeld. The mother get 100% and the father has to pay his full maintenance.
So be warned boys, a German shag is good, I say very good, just like those nice video's we see. But for the final cost you can get a lot of bad sex elsewhere. And we know everyone likes 'bad' sex.
As a lighter option, get a buy-to-let mortgage, buy a house and invest the same amount of money there. This way you will have something when you retire.