I think there's a big difference between nasty hill climb style climbs in the UK and long linear ones in the French alps. Weight is all about acceleration, so if you're just keeping up a nice tempo going up the galibier I would say weight is less important than riding steep lumpy stuff where you have to change speed all the time.
You have a finite amount of gas in the tank. It takes some of that gas to move a dead 1kg 1,400 meters vertically. Or 3000m if it's a big day. So don't carry the 1kg if you don't have to :)
I think there's a big difference between nasty hill climb style climbs in the UK and long linear ones in the French alps. Weight is all about acceleration, so if you're just keeping up a nice tempo going up the galibier I would say weight is less important than riding steep lumpy stuff where you have to change speed all the time.