Feeling lonely in London.. Suggestions of ideas on what to do?

Hi I moved to London at the end of 2014, to start a new job...which I love. However, what hasn't been so easy to figure out is how to create and build friendships in this transient city. I've done the following so far:

1. Meetups: I've to a lot of these, but as is the nature of London, you go regualrly and never see the same people twice.
2. If you do make connections at these Meetups it takes weeks, maybe a few months to organise something, for example, cinema.

My work colleagues don't socialise outside work.

Find it incredibly lonely here, everyone's so busy , cold here - stop and ask for directions, people just walk on by!

Any suggestions?