That's the one. I wouldn't get too concerned about i-size because if you stick with rear facing seats, they'll either for the isize criteria or be better than it.
If she's above the 50th centile for weight or height and you're keen to rear face up to 4, you'd be much better looking at the 25kg seats such as the Axkid Minikid and Britax Two Way Elite. They don't spin but they're much better seats. Th Minikid is Swedish Plus tested so a much stricter test than isize.