Having tried my usual methods (SuperOneClick & Flashtool) and after a conversation with a Sony Rep, I have found what may be an issue stopping rooting, until a workaround can be found. Namely the Internal Storage is locked by default to MTP. Clicking on the Drop Down box, which used to be used to switch modes, only offers an explanation of the functions (ie MTP & MSC), but will not allow switching. Apparently this is now standard on ALL new Sony Xperia's, probably in order to stop rooting! If anyone has found any other methods, without disabling MTP please post a reply. Thanks.