I do sympathise with you, and if you're this unhappy, you're definitely right to do something about it. However, getting your husband to quit his job and relocate is pretty drastic, so if you're going that far, you're going to have to be really certain of what you want. I'm not sure from what you say that London is really the answer.
I've recently moved up North after 28 years of living in various bits of London (and I agree with you about the areas you mention being splendid), but the truth is I also have lived in some seriously grotty parts of London that could make Stockport look like paradise. When I was working in London, I had a fairly decent job and income, but still ended up in a small flat in a rough bit of zone 5 - it wasn't much consolation to me that I could go to the posh stuff in the centre, because it took me a very long time to get there on the tube and at the end of the day it's what you're living in when you step out of your door that has the power to affect you more. Later, I moved to Hammersmith and worked in Docklands, and it took me 1 3/4 hr commute everyday, which is almost the time it would take you to jump on the virgin train from Manchester to London, so if you're feeling you need a fix of the good bits of London I wonder if you really need to move there when actually it doesn't take that much longer to commute in than it does to cross the city.
If you dislike Hale, I think a lot of the property in London would depress you a lot more. The choice then is you either move out to zone 5/6 and get something residential, which probably would also feel a little dead, and you'd still be about an hour from central London. Or you buy a very small flat in central London, and accept the fact that you've got no space. It can get quite claustrophobic. The dream of living in London may well be tied up with living in one of the really chi chi bits, and if you have a look at rightmove.com, you may find the lifestyle you really really want wouldn't be possible anyway - I don't know if that's a consolation, but I'd hate for you to move to London imagining Kensington and ending up in Canning Town.
Is it specifically London that you're wanting, or is it more that this area isn't working out for you? And is it really the whole of the North-West or is it just this bit? If you explored more, could you find some corner that you'd click with? Could you move further out, and your husband commute? I think if you can put your finger on exactly what it is you think you're missing, you might be able to find a formula that works for you without having to uproot quite so much. I wish you lots of luck, and I hope you find what you're looking for.