Just to balance the (natural) bias of people piling on to say how ace London is, I'm one of the people IBorgia claimed didn't exist: I have a child, live in London and am desperate to move out. It's not that I live in a bad area, I don't, it's leafy mc suburbia here. I like my tiny patch reasonably well. It's the wider city I detest.
It's the stupid stupid fucking housing market, the lack of space (we have an excellent park, but that's not the same as proper space, it's the dirt, the noise, the horrifically crowded public transport, the endless hordes of tourists making areas almost impossible to visit. It's the bars, pubs and restaurants in town being overcrowded and noisy and dirty. It's the cost of parking, drinks, coffee, everything. It's not having the space in any nearby cafe to bring my buggy in, and having to fold on buses/missing trains because you cannot squeeze on, and no one gives a shiny shit that you might be standing in the pouring rain with a small child. It's the 'me first, mine, fuck you' attitudes (I'm talking mostly about the city proper, not the 'burbs).
I've visited three museums in the last year. You always think/say you'll go all the time, and somehow don't. Of the three, two were in town (NHM, Science Mus), and had to queue for 40 and 50 mins to get in, had to queue round the dinosaurs exhibit, had to queue to eat in both. Not a magical day out.
I moved schools 14 times between 5 and 18, including twice overseas, and loved it. I'm not anti moving at all, I just cannot for the life of me understand why you'd move back to this horrendous city. I cannot wait for the bubble to burst and everyone to flee like rats from a sinking ship.