It appears that recently email synchronisation is hanging "quite regularly" (at least daily) - this leaves the notification on the lock screen, but stops all the email accounts (Windows Live, Google, Outlook (i.e. Exchange) and two POP3 accounts) from downloading new messages.
At first I thought this might be because I was reading my gmail using the Windows 8 mail client on my laptop, but it is now being seen to happen when my laptop is asleep.
It appears the only way to get any notifications working again is to reboot the phone, which is slightly annoying, as it loses the information on the currently playing album/track.
Is there any way to find out the cause of the hang, or is there any mechanism to abort/retry the synchronisation? (even better if it could report the crash to Microsoft)