Thank you both!
Mon77 - thanks very much for the link. I'll be treating it like a long run too, it will be my first 20m of training, so I want to use it to play around with pace and hydrating & fuelling.
Laps aren't my favourite thing to do (and I've been put off even more by recent forays into the world of sprints and speedwork!) but running in a race environment, even if I'm not actually 'racing', is a good way to keep me motivated! 
Wilkie - thanks for the tip about Majestic, I think that might lure a few more friends & family out to support me! 
Edited: 13/01/2012 at 14:26