zafira wont start of the key?

What engine?

Is the engine turning over on the starter (check the auxilliary belt is moving when starter running) or is the starter just spinning?

I'd suspect that, for some reason, the starter is not spinning the engine fast enough to start.

Do you have the correct battery fitted and have you tested its voltage and cranking amps?

Have you checked the wiring and earths at the battery and starter motor?

Did this problem just suddenly occur, or did it get worse over time, or did it appear after other work was done on the car?

The starters are known to get choked with dust, worse on some engine types than others.
Those with dual mass flywheels seem to be worst, to the point that garages will not give warranty on a new starter unless a new DMF is also fitted!!

fred
August 2011