Lachie,
Welcome to the forums.
Glad to hear we've been of assistance to you
MCE does a guide download at a time which can be controlled. Can't remember the tool off the top of my head, but have a look around and I reckon you'll find it. The alternative is to go to the guide section under TV via settings and do a manual download (goes and grabs the local BRP data).
However if you don't touch anything MCE will on it's own accord grab the latest data, I've never felt the need to play around with MCE's EPG download time as the guide is always good to go when I'm using the box in the evenings and If I'm mucking around with it I'll kick off a BRP download then do a manual download via the GUI.
I hope that helps.
Cheers
Matt.