Cold spots would be much more likely to form when the metal screws come into contact with the plasterboard, so you are much less likely to get this problem when the screws are kept out of contact from the boards.
Woooo - a statement of the bleedin' obvious! So, as long as you leave a 5mm air gap betwixt the ice-cold steel screw head and the back of the p'board, all will be fine...
I hope Kools uses foil-backed p'board, 'cos another thing that will likely happen (unless he doesn't boil kettles - or breathe) is that the moisture-laden air in this room will penetrate the p'board and condense out on the vapour membrane immediately behind it as it hits that ICE COLD 5mm air pocket. Cue - dozens of dark damp circles... Dee-DEEE-dee-duuuhh.
'5mm air pocket' That got quite technical, my point was simply bury the screw head a few mm in when you fix the batten
Well as long as I'm not the person paying for materials.... A days work at best for me. And logic would suggest buried screws would cause less cold contact with the PB. You could always use Stixall......
If I were doing this work myself, It would be as kool has done. But I'd probably get my handy man in to help and put up insulated boards (D&D + mechanical fixing) since he has the experience to ensure the boards would be straight.