In Berlin there's St. Oberholz: http://www.sanktoberholz.de/ which has really embraced the people using it as an office. Feels like a very welcoming place when you have to get some work done and you won't bother "normal" people since everyone knows what the place is about. They even have added a better co-work space with more office services like snail mail, scanner, printers, conference rooms etc.