brake light not working . faulty fitting?

My new series 3 is proving to be a nightmare, can anyone please help .Brake lights aren't working . bulbs are find . Switch has been bypassed in order to rule out and still they don't come on , fuse is fine however passenger side fitting is cracked and it isn't touching both connectors on bottom of bulb . would this effect both lights . It was working when I picked it up on Sunday but then again so was the gearbox!

Multimeter time.

Do you have +12v at the switch (ignition on)?
Does feeding +12v to the other switch terminal put the lights on?
Do you have +12v at the bulbholders?
Do you have a good earth at the bulbholders?

A duff fitting on one side won't stop the other side working, no.

Take the bulbs out and give the fitting and contacts a clean. If brake lights still dont work then check the wiring, could be an earth fault