So is Chelmsford
But seriously. If you're an independent trader then where you live will could in theory be anywhere (optimised for quality of life, cost, and tax system), but will also have some path dependence. A lot of succesful traders, in my experience, are ex industry professionals and are therefore likely to live in or around London. Essex in particular is a hot bed of ex-LIFFE traders, and a few trading arcades continue that tradition in a small way. I live where I live because I used to work in London (many moons ago I did live in London as well), and now with kids at school.
I can't understand why anyone would want to live *in* London unless they're working there, or they extremely rich and enjoy the attractions of living in the city (which I don't).
If I was starting completely from scratch (without the path dependence) actually the UK isn't a bad place to be. Away from London it's not as expensive as say Norway, there are some nice places to live if you choose carefully, the schooling and healthcare is free and good, and the tax system is pretty friendly for a developed country. I used to live in Dubai, and I'd certainly rather live in the UK.
GAT