My Vauxhall Corsa Nreg cut out after making some rattling noises, now it wont start or even crank?

There was a faint burning smell under the hood. If an Immobilizer has cut in would the engine still crank - im getting nothing. Cam belt seems ok|||If the smell was burning rubber I would still suspect the cam belt. If the belt has broken the pistons will have hit the valves and will prevent the engine from turning over.