The best solution I've come up with is entering the following commands:

gconftool -t int -s /system/osso/dsm/display/display_dim_timeout 0
gconftool -t int -s /system/osso/dsm/display/display_blank_timeout 0

The screen still dims but it never turns off. That's a good enough solution for me. The only last thing I'd be tempted to do would be to have the screen turn back on every so often but I think I read earlier that there is no cron on the N800 so not quite sure how to go about that.

I've managed to get SSH tunnelling working between my machine and the device, it makes is so much easier to edit stuff!

Thanks