Norwegian (5 Troop) medals

My Grandfather was a Whaler and was at sea when Germany invaded Norway. Upon landing in England he joined the Norwegian Army and then was selected for the Commandos.
I remember seeing his medals when i was a small boy but alas they have been lost.
My question is how can i go about finding out what medals he was awarded? I suspect he may have had medals from both the British and Norwegian military so where do i start in my quest?
Thanks in advance for any help.
Richard Calvin