When I first moved to London, I lived in Farringdon and then Marble Arch, and the first couple of years it was awesome to be able to just step outside the door and be in the centre of town (at Marble Arch I literally had two minutes walk to be on Oxford Street, or could cross the road and be in Hyde Park). But the pollution was certainly awful - it's the only place I've lived where your snot would be black at the end of the day. And then I moved to Barnes (South West London - very leafy, very affluent), but when we decided to buy it was too expensive, and we ended up moving to Croydon (zone 5, South). I don't think I'll ever move closer in towards the centre again. If I were to consider moving elsewhere, it'd be either further out, or along the edge of London somewhere along one of the major train lines.

You get the option of working in the centre when it makes sense, it's far more relaxing, greener, far less pollution, and far cheaper.

I can see the appeal of moving somewhere else entirely, but this is a decent compromise for people who want easy access to London but don't want all the downsides of the centre.