Doh! Refill it when the car is cold, burp it with the top rad hose and the header tank cap off. Then put cap back on run it up to temperature whilst watching the temp gauge.
Make sure coolant circulates through the heater matrix by setting the fan heaters inside the car to hot with fan on. Make sure air comes through warm.
Check the fans on the radiator kick in when its up to temperature. If you still have a leak, it should show itself pretty quickly as the system pressurises...
I did a coolant change recently on mine and read that a good tip is to slowly fill the system from the hose that comes off the back of the header tank to the turbo. Just unplug it from the header tank and slowly fill with a small funnel shoved in the hose end. This allows the coolant to effectively fill from the bottom up and minimise risk of airlocks. Pretty much as per
http://www.type-ra.com/subaru-forum/...e-guide.19670/