I can't resist the lure of a personal question or three..

I've only ever lived in SE/barely SW London (except for a stint away at uni) so can't really comment on living in N London. If money and proximity to family were no object I'd probably decamp back to Herne Hill, which I loved (though that was in a different pre-offspring life, perhaps I wouldn't love it so much now..).

My impression of N London is that it's awfully flat and not very green. I love a nice view, and we have them aplenty round these parts.

The things I'd change about SE23 would be the south circular, which I think stops the centre of Forest Hill from being particularly nice. I much prefer Sydenham, even though the high street is a bit shabbier. But more importantly I'd make it cheaper.. am currently facing the prospect of having to move elsewhere as I just can't afford to move anywhere bigger and stay in the area. Am gutted to say the least..