Thanks Xopie, I've tried that, I have it ticked. There's also a recommendation to untick all options on the Outlook icon right click menu, close Outlook, reopen it and retick the desktop alert option. It still doesn't work for me.
One of my problems is that I'm using an IMAP account as my main mail account. Since that account is provided by my ISP, changing it to using POP would, in theory, fix everything. This seems to be the cause of the issue, the problem only occurs to those using IMAP.
It's been suggested that applying SP1 to Office 14 fixes this, but I haven't tried that yet.
There's a very extensive thread on this topic at
http://social.technet.microsoft.com/...5-cd4ab8b8319d
It seems that this issue is a lot more complex than one would think. And I'll reiterate my main issue with this, again: it is ironic that Microsoft so proudly display a mail notification tile on a Windows 8 home screen.
Hopefully SP1 will fix this, I'll post back when I find out.