I've used satinwood paint on rads with good results. A water based paint smells less than an oil based paint. I just cleaned and lightly rubbed down the old paint with wire wool. Make sure the rad is cold and leave it off until the paint is completely dry.
Just started painting dd's room, and as we are using matt paint on the woodwork, thought that the rads should be matt too. Is this do-able, does anyone know? Do you have to sand down first? Any comments welcome