I think the pain of leaving London is a matter of personalities and interests. OP does says that sheh is fed up, so obviously not all has been wonderful, as far as her aspirations went.
Jodie, you do sound, otoh, like someone who should stay there. Very extravert and boho/alternative. Mind you, I'm surprised that Spero isn't mentioning that Bristol has Stokes Croft and street art and many international places to eat arouond there and Gloucester road - it's really not miles apart from Hackney but on small scale and more peaceful. Other places - I'm not so sure, don't know of any that's strongly alternative - I mwan in a creative sense, not just crystal healing
. Bits of Manchester maybe but I haven't been there.
Also, if you are relatively young, who knows, you may go back Jodie, at some point. Maybe you'll win something or inherit, or your kids become vey succesful. I think if someone would only go back if they could afford a huge house or live only in rich area like Hampstead - isn't really THAT much in love with london. Some people over 40 live in a 1-bed if they aer glued to the place - usually those with a huge social life.
But my poibt is, if your interests lie in nature/peace/painting outside, animals, then movinbg from London is relatively easy - also imo if you aer not so extraverted and crave some peace and don't like constant crowds everywhere you go. So there is no one rule for all.
I've moved out but now decided that I am too far. I'm genuinely happy to be away from london for half of the week, but I do want to be there weekly. Lived there for 20yrs and love it overall, but do not love all the areas, or some dullard suburbs. If I was offered to live in a depressing area of london (or criminal one), i'd go without question to a beautiful smaller place with history and nature around. But if I was offered my preferred places (which I see as home still) I'd of course go and lilve in london. Obvoiusly can't afford those now and wouldn't live in a shoebox. You have to be open-minded really, not just be negative.
I do think it's important that you find a new place attractive, something there that you love. Don't chose for purely practical reasons.