First post, and its a doozy!
I've got a '96 300 tdi discovery, which has recently developed a very bad habit-starts first time, but after a while cuts out, and won't re-start. If I then leave it for a while (half hour) it will then start again. the last incident, it had started fine, drove for 20 miles, stopped at a shop in the village, and then wouldn't re-start-walked home in the rain, walked back next day and again started first time
any ideas what may be causing this??
David

when was the last time you changed your fuel filter ( on bulkhead )
and have you checked your sedimenter !! behind rear drivers wheel tucked in behind chassis

When you say won't restart, does it turn over properly but just never fires?

turns over, but doesn't fire-first time it happenend, flattened the battery (now carry fully charged spare and jumpleads)

Robint-serviced 3 months ago-would they chack this as part of job?

Could be a small crack in the fuel pick up at the tank end which slowly lets air into your fuel system. They can rust quite badly without you knowing and get pin sized hole in which over 20 miles will allow sufficient air into the fuel filter to give an air lock when trying to start. Next time you have it running undo the bleed screw on the top of the fuel filter housing and make sure doozel comes out easily (dont undo too much), this will bleed the system up. Then if it does fail to start again open the bleed scew again and see if air comes out. If it does it will most likely be the fuel pipes. If not and you have fuel there right away it might be dirty injectors or wear to the injector pump. Doozels are quite basic really. They only need diesel and air to run and a bit of heat in the cylinders to get them running (glow plugs). Let us know how you get on.