Ez mate, I'd never pay to use a studio to practice DJing, whatever they charge you wouldn't be worth the money as you're gonna need hours and hours of practice and would pretty soon rack up quite a big bill! You'd be much better off saving up and getting a very basic setup, I'm sure there's plenty of decent deals out there atm to get people started up, especially around Xmas time.
If you are looking for something free though maybe ask around at some local youth clubs? I can imagine they might have what you're after somewhere if money is really tight.
Big ups