iTunes has been pestering me to update iOS 7 to fix that pesky lockscreen bypass glitch, so I let it update, and
now it has disabled the lefthand buttons on the lockscreen keypad - 1, 4 and 7 - two of which are part of my passcode.
So, in fixing the bypass bug I've managed to remove the only way to bypass my freshly borked lockscreen. Of course, I can just restore the phone back to an earlier backup... no, wait... iTunes won't backup or restore a backup image to a phone while it is locked. What the actual f**k?!