I guess the better question is... of these, which are you attending... some, all?
XBIZ EU 2012 - London, Sep 16 - 19, 2012
http://www.xbizeu.com/
Webmaster Access 2012 - Amsterdam, Sep 21 - 24, 2012
http://www.webmasteraccess.com/
The European Summit Fall 2012 - Prague, Sep 24 - 27, 2012
www.theeuropeansummit.com
Oktoberfest Gathering 2012 - Munich, Sep 30 - Oct 02, 2012
http://www.oktoberfestgathering.com/
?
I'm leaning towards the top 3 - xBizeu, Webmaster Access and Prague...