No hot start

Scudo 1.9 Diesel van year 2002.
Starts first time when cold in the normal way.
When at normal working temp, switch off engine do a delivery about 7/8 min try to start it the way you would a hot diesel, the engine will turn over but will not start.
The only way i can get it to start when hot is to turn the key to the position that turns on the heater plugs (glow plugs) let the dashboard heater light go out wait a further 5/7 secs and then turn the key to the start position and it will start, it will do that all daywith as many as 60 stops and starts.
Any ideas would be welcome.
Regards
tribalreaprr