I went with a local jobs board and found a job as a mate with a JIB qualified Spark at a big site. I found it helpful also to get around any sites in your area and ask for contact details to whoever is handling the electrical installations. You can try asking at the gate for a site manager/supervisor and if lucky have a chat with them about who to get in touch with.
One you get your foot in, just network with people, whichever trade it may be. You never know, maybe they know someone needing a mate/improver.
Also check the big ones like Hays, Sparkings, Reed and maybe register on LinkedIn (I found some interresting offers).
Good luck!
P.S.
APPLY FOR AN ECS CARD, PRONTO!
Could not get anywhere without that, although some people say they could find work with a CSCS. Either way, and ECS card will give you some more credibilitywith the big employers.