Gtksourceview editor should pass ctrl+pgup/pgdn events to the containing notebook so that it works the same as the scintilla plugin.  At the moment ctrl+pageup/pagedown move the view across one page which is pretty useless and there seems to be no way to switch between tabs.

Other information:
A more long-term solution is to put these as actions so they can be customised as shortcuts, but this would be a lot more work.