I'm actually joining up Peak tomorrow because the gym we have at our complex no longer serves my purpose. It's not the best and doesn't even come close to what I'm use to back home.. **sigh** NY Sports Club. But it serves it's purpose. there is a £20 membership fee and is £51 a month. And you can pay as you go monthly, doa six month deal or a year. Which ever you prefer.
There is also a Reebok at Canary Wharf but the prices are exhorberant and borderline on grand theft
But I heard they have lowered their prices and are very much in trouble. That's probably where I'll end up (if it does't go belly-up first) since there may be room to negotiate prices. Because Peak Fitness is not really what I'm looking for but is very close to where I live - so it's convenient.
You may want to try this link: ftp://http://www.gymuser.co.uk/london/gyms-in-london.htm
ftp://http://www.peak-fitness.co.uk/index.html