Diesel wont start when hot

[mig]

Finally got our leisurely paced petrol to SB (1.6 TD)conversion finished and out for a long-ish run at the weekend.
Seemed to run hot-temp gauge just over 3/4 -I don't know if this is because the gauge is still from a petrol van?(used to run halfway when a DG was in there)
Stopped after 6 miles to check everything was O.K,wouldn't sart without 20sec. glow plug burst-slightly surprised as it was nice and hot.
Stopped again after 30miles,bought ice cream.
No way would it start,spinning over well,plenty of diesel from the leak off pipe.
Had to call out the breakdown service.Fairly useless guy turned up 40mins later with a recovery truck and no tools,wouldn't even attempt to start it and towed us home
Tried to start it a couple of hours latter after I had stopped crying (and everything had cooled down)and it started first time.
Anybody any clue what could cause this?
This a fairly basic engine similar to a JX,the glow plugs just work off a push button -relay no temp. sensor to reduce the time when it is warm
Thanks

[Oldiebut goodie]

Did you try the glow plugs when hot also did you try the cold start? Some engines seem to like a little assistance when hot for some reason. My last CS did. The current 1Y engine has the temperature sensor maxed out so that the plugs always come on. No harm is caused just shorter life possibly of the glow plugs.
Also the normal position for the temp gauge on mine is 3/4 all the time - just need to change the sensor but I know for certain that it isn't overheating so have left it.