@Pipsquiggle I think in that case one OOC catchment child would simply displace one Bucks child. I do agree, it would drive me round the bend if I lived there.
The Blue Coat school has no catchment at all - if a London child sat the exam and was in the top 180, they'd simply be offered a place. This means we do get kids commuting from Preston and Warrington, which breaks my heart for those kids a bit - it seems like such a long day. Kids are put in either group A (definite place), B (reserve list, ranked) or C (very unlikely to get a place).
The batshittery in Liverpool is the fact that over half our schools are religious (a remnant of Northern Irish immigration) which means popular non religious schools are very very oversubscribed. Because the Blue Coat takes only 180 kids from a population of ~5000, it has a reputation as being very hot housey and competitive (not sure how true this is - it seems much less competitive than London schools). I know a lot of parents who really want their child to go to what is essentially the local comp, but sit the Blue Coat exam as back up.
The plus side is that, because we don't really have private schools and only one grammar, there are a lot of bright kids who go to normal schools. The downside is that competitive parents go to church for three years or move into catchment for popular schools instead and the unpopular schools suffer as a result.