I have both a 200 and a 300tdi that are now both happily running on bio-diesel at 90p a litre (woo hoo). The onlt problem/setback ... and it seems a very minor one, is that the idle speeds of both vehicles have gone up. I've been poking around the Haynes Book of Lies but I cant see an easy way to drop the speed back to close to factory standard. It seems to have put a good couple of hundred RPM on both trucks.
In both cases the adjustments are easy and quick.
Get someone to sit in the 200tdi first, engine OFF.
Open the bonnet and look at the top of the injection pump on the right (driver's) side of the engine.
Tell your assistant to press the throttle pedal to the floor and back up again, not too fast, till you tell him to stop.
Spot the plate thing on top of the pump that moves back and forwards as the throttle pedal goes down and up.
Spot that BOTH sides of that moving plate thing end up hitting screws with locknuts when the throttle is fully DOWN, and also fully UP.
The screw you need to adjust is the one the throttle plate leans on when the throttle pedal is all the way UP, as in NO throttle, tick-over.
Undo the locknut and back the screw OUTWARDS just a little, say half a turn.
Start the engine, and adjust the screw till the tickover is as you wish, about 700 rpm being good.
DO NOT interfere with the other screw, as that will let the engine reach higher revs. This serves no useful purpose, but risks over-speeding it, which could have disastrous effects.
