Hi first post here, had my Focus about 5 years and have just replaced the headlights as the plastic fogged up so bad not much light came out.
I replaced them with headlights from NP Autoparts, but now the sidelights dont work. Main beam and dipped work fine and the sidelights come on when on main beam.

Is it likely that the headlights have been wired wrong as the side lights worked fine on the old headlights. Rear lights still work fine.

 

You have pattern headlamps and they have probably got bad contacts on them internally. We have had that problem lots of times in work.