Both nice ideas, but you need the rad to be stood off the wall a decent amount to do either. In the lounge we have to bundle the curtain up on the window sill or cover the rad and in the bedroom we can't even do that - the sill's too shallow. This isn't the 1st house I've lived in where that's the case.
You'll lose a lot less though - the rad heats the inside of the wall (feel it!) and so the temperature gradient is much greater than across a wall at room temp.
Chris