My tuppence would be to attend events and meet people in person... as once you've established a credible relationship it's easier to convince a potential employer to give you a shot.

From their perspective it's about risk. Commercial experience de-risks you as a potential hire, but so does a relationship, even a new one.

If you make it to London get in touch with me and if I can help I will. My email is richard dot marr at empora dot com

Edit: another route would be to take part in open source projects with a strong contingent in London.