Actually, I managed to get this all sorted out.
I cut the little pin off that shuts the screen off when the laptop lid/screen is closed, I also turned off the screen with the Fn + F5 command.
I also bought one of them lap-top cooling pads and it is sitting on that, it's running a LOT cooler than it was when I was using it as an actual laptop.
Has anyone used an older Dell laptop lately sitting on thier laps and realised how hot they do get?
Good point about the keyboard forming part of the heatsink,
I left the keyboard in mine for that very reason.
The only thing I have left to do with this computer is work out how to make that annoying "Your computer may be at risk" nag bubble from appearing, now that I've turned Automatic updates off.
This computer is not connected to the internet or to my network, so I don't see why I need security updates.