Well, if I go back to work we'd be in this category, and I'd want to know if the state primaries are going to charge like the preps (and at £15k as per the suggestion in the article, the state schools would be more expensive than the local preps), are they going to provide the same level of service? are they going to limit fee paying class sizes to less than 20, ideally 15? Are they going to provide music classes, a range of sports (with the facilities for them), before school clubs for every child starting at 7:30am, after school until 6pm with enriching activities in that time, not just childminding, and all included in my fees?
Are they going to be strict on discipline, removing any DCs who create problems quickly?
Right now, we aren't going to privately educate (we actually can't afford it, even on those wages), but if I was going to have to pay for it anyway, there's no way a state school, no matter how good, can compete with the bulk of the private schools in the area.
And yes, the assumption does seem to be that good schools in expensive housing areas are good independent of the area/intake and that house prices only are higher round there because of the school. This might be true in some parts of London that previously were dodgy areas, but outside of London, it does seem to be that the expensive areas containing the outstanding and over subscribed schools have been expensive for a long time.