Vauxhall Tigra engine cut out, will turn over but won't start,

Check timing belt .

the clunk before the engine cut out would suggest snapped timing belt,you need to remove the timing belt cover to investigate further,if the belt is ok and timing is ok then do a compression test,check for fuel and spark etc

I would agree with 2145simon sounds like the timing belt.Get it checked out before trying to start the vehicle again as if the belt has gone then everytime you try start the car you can cause a lot more damage as the vauxhalls engines dont take much before they decide to start doing valve damage etc.

thanks lads ile have look tommorow.

Timing belt is fine, checked plugs and they are sparking ok, checked power is getting to the fuel pump, still won't start, when i checked the plugs i could smell petrol on them.

remove the plugs and allow the cylinders to dry out and dry the plugs,have you checked the compressions as suggested before

When trying to start the engine is there any strange noises coming from it as i dont realy no what you mean by a clunk but im assuming its something internal in the engine so get a compression check done on each cylinder then if all is ok we can work from there.Might be worth getting under the vehicle and giving the cat a few thumps with your hand as it may have collapsed which will then stop the car from starting.

you say timing belt is ok but have you actually checked the timing?

As " paulieone " suggests , timing could have jumped for any different reasons .