Car not starting

Hi I have a problem with my skoda fabia 1.4mpi. It was turning over and not starting we looked at various things that it could possibly be. The oil sensor had gone so that got changed plus spark plugs. It was getting fuel and spark, thinking the most likely cause was the head gasket we changed that. But it still won't start...it would try to but sounded like it was trying to go backwards it would then just cut out. Can anyone help? I really need to get it back on the road!