Dolly - I think you are going to tie yourself up in knots the way you're agonising over this without having set foot in the state schools (and presumably gone through the private sector as a pupil yourself?
I think people have tried to be very reasonable with you, and given you good advice, but tbh you seem to be becoming more entrenched.
If you are going to spend the whole time your children are in school agonising over whether they are 'aspirational enough' or mixing with the 'right types' etc then frankly I'm beginning to feel that you should remain with the status quo. It seems like you have a fundamental fear of the state sector. I hope you don't pass that on to your own children, as 93% of kids go to state schools,so it's likely your kids will come into contact with them at University and work!! And remember, your own children may well not be able to afford private school fees for their children, so hopefully they won't think it's their only passport to success.
It saddens me, because there are so many MNers on here who are state educated, often at schools which sound far inferior to the ones in SW (I know mine wasn't great) but we are literate, numerate, have successful careers, interests in politics, the arts,etc etc...... But to go back to what I said earlier, some people have a fundamental lack of confidence in themselves as parents to encourage aspiration in their children, or a fundamental lack of confidence in their children's innate ability, and if that's the case, maybe paying sets your mind at ease.