hi from the UK

Welcome!  Look at the Aggressive Couch to 5k plan to possibly build up your running as you bike and swim.

Pending on how your running progresses, an Olympic near the end of the year isn't out of the question.

Good luck!

Hi Aslan.

Welcome to the site. Lots of friendly folk on here. Even if they are mostly American  

I'm a Londoner too. Did my first Triathlons last year. 2 Sprints and then an Olympic Distance in September. My background was similar in that I cycle a lot, swim pretty well but struggle with the running. I actually followed the plan Ron mentioned to get in to running and although it seems very conservative to begin with, it had me running a 23 minute 5 K at the end of my first Triathlon AND I didn't get any injuries.

A very good beginner event in the London area are the Thames Turbo Sprint triathlons :

http://www.thamesturbo.co.uk/club/

Very friendly and a pool swim.

And the Olympic I did was this one which they are doing again this year:

http://www.f3events.co.uk/race_view.php?i=13

It's in the rowing lake they'll be using for the Olympics, so it's clean and the bike leg is on closed roads.

If you have any questions send me a PM and other than that: Good Luck. 

 Thanks for the great replies. I have now entered a sprint Triathlon at dorney lake the end of may and hopefully I've entered the mazda london olympic Triathlon in August competing on behalf of Sparks.

                                   I've done a couple of Runs this week that went pretty well, 1 swim which went very well I tried some new techniques which I got from a dvd and found I was in much better shape, it's early days but I'm happier than I was. I also did a cycle and have now got a route mapped out including 1 big hill and a moderate 1. For now I'm aiming to do 1 cycle, 2 swims and 3 runs a week.