There are a few at House of Divine. I've enjoyed Danielle (mixed-race Mancunian), Chloe (Essex porn star Karlie Simone), Seven (Essex Caribbean) and Apple if an Oriental (Filipina via Singapore) does it for you. None of these are stick-thin though, Apple is probably the most petite. There are other Brits there that I haven't met. Also some more that aren't EE, like Brazilians. You'll likely get a few mins cut from your time if they're busy, but the price is fairly competitive for C London.
A lot of Brits are with the £200-£300++ agencies, I don't know if these are any better though.
Hopefully some guys will be along to point out a few top-class Brit indies, but they aren't as common as you would hope in London. You're probably better off in the Midlands & North for English girls.
