i'm german but livin in the UK now. there are so many charity shops and 2nd hand shops here, but it is quite hard to find any in Germany. like Veri said, there are some fleemarkets but that's it. no thrift stores or charity shops.
have a look at myfabrics.co.uk - they are based in Hamburg, i think they are not too cheap but sometimes you can get some nice bargains. and they send you free samples. and they deliver for not too expensive cross Europe.