I can only suggest that you visit nice forums like
Sportsbikeworld aka
http://www.sportbikeworld.com
Cycleforums
http://www.cycleforums.com
etc.[These two are the best, btw]
Read, read everything they have to say about newbey bikes.
Biking is very differnet than cars, more so on London roads where:
a) Roads are frequently wet an slippery.
b) There are a few thousand jokers who are riding like idiots just so that they can save some money because of new schemes. They ride so pathetically they are a hazard to everyone in vicinity.
Whatever you buy, ride safely and ride with the thought that everyone else on the road is out to kill you. You'll survive. hopefully.
EDited for links. And yeah, don't let peer pressure dictate your choice of two-wheelers. You don't necessarily have to buy a bike as well. There are plenty of moto-scooters from Yamaha. Honda, Suzuki. Very fast, enjoyable and very practical for city riding too. Sportbikes can be annoying in city traffic. Just keep an open mind. Don't rush things and become another r6 squid if you get my drift.