vauxhall zafira 04 2.0 dti intermittent start when warm?

my car has intermittent starting problem when warm after stopping off for short stop get back in car and if spanner light does not come on ,car will not start and front engine fan starts up!
turn ignition on off til spanner light eventually comes back on !
New glow plug and heat sensor vauxhall cant find fault!

thanks mark