So far during the Vista Beta the extender functionality for Xbox 360 has been limited to the US and Canada. However the recently released 5472 build of Vista has opened this up to other regions. Unfortunately you need to be a member of the tech beta or MSDN (en_windows_vista_beta2_July2006CTP_x86_dvd.iso) to get access to this. Currently the next public build that will include the European functionality is RC1.