Well to stop that heat getting out simply stick some masking tape around the edges of your windows :)

This is exactly what I've done with a window in my hallway this winter. It's the original victorian metal frame and even when its's closed 'tight', you can hear the wind blowing in.

Caulk.

I don't think you quite understand how double glazing works. But let me say, it is well worth it.

And it has fuckall to do with keeping air from coming around the edges.

The stagnant air between the panes makes for a really shitty conductor of heat, air being one of the best thermal insulators, short of hard vacuum.

Think of how a thermos works. Same principle.

And it has fuckall to do with keeping air from coming around the edges.

I think he meant if you're too much of a cheap bitch to have it installed.