Check the bloody timing, it's easy enough to do.
What color is the smoke coming out the back ?
Black is over fueling (but generally only when running)
Blue is burning oil (engine oil not diesel oil)
White is unburnt fuel, I suspect this is what you have.
Now if the cam belt has slipped the timing will be out, it maybe out just enough to stop it starting due to lack of compression or fuel being injected at the wrong time.
There's been quite a few threads on here about 300tdi's not starting, and quite a few of them have been down to timing.
It's very unlikely that you have lost compression in all cylinders overnight, and if one or two had low compression it would still fire or try to.