There are a lot of jobs going in london, contact encore energy and I know rig energy were looking for people in london, keep an eye on jobisjob website, see a lot down south on there.
You can make good money in london, I worked london in january for a month and averaged out about 500 a week but now that the work volume is higher its likely to be more now.
With regards to training when you speak to these companies if you havent got any electrical experience I would just say you have a little experience as a sparks mate or something and the fact you fit gas meters gives you an edge as a lot of companies want duel fuel techs, its a good job, ive done it for a few years and enjoy it, made more money than I would have as an average sparky, as ive said on a lot of posts dont listen to some of the muppets around that say the job is lame and boring, there are a proportion of guys out there i.e ex meter readers fitting meters etc and these are the guys that give meter techs the stereotype that everyone in metering is thick as ****!
Half the lads I have worked with are electricians and gas engineers like yourself and I think the minority that slag off the industry are your average sparky who probably hasnt been given the opportunity to get a crack at the job, the spark industry is ****e now anyway and the bulk of work going about isnt any more interesting than metering so give these companies a call, pretty sure you will get somewhere with your background! Apologies for the long message! lol