It's lottery allocated now to stop people moving into the catchment! These days even if you live in a tent by the entrance you're not guaranteed a place. You stand a better chance if you're within 1km as that's 'inner zone', but even then it's a long shot.
It's clearly a v.good school with a lot to offer and I know kids there who say they're happy, but you have to bear in mind that it's incredibly strict (kids aren't allowed to talk between lessons, detentions given for just turning your head in class, etc, etc). It depends on your child and whether you think that's right for them or not. We didn't go for it.