My 5-year old daughter wasn't with me when I bought this coat, but we'd bought her a waterproof coat form Mountain Warehouse, and I was confident that the size 5-6 would fit her properly. She is happy with the warm fleecy lining especially in this cold weather.
I'd checked the various ski jacket reviews on this website before going into the shop, so I knew to test the zip carefully before purchase. The zip works fine. The only reason this review is 4 stars and not 5, is because I think the hood seems a little small in comparison to her waterproof coat . It covers her head, but seems to stop very close to her forehead - it isn't a very generous overhang peak compared to her waterproof coat. The coat does say that it doesn't have taped seams so it isn't fully waterproof in a downpour - but it would do fine for our purposes.