Hi, I ran my 307hdi 2.0 on biofuel for around 18 months with no ill effects at all, cold starting was not as good but i just started mixing the bio with regular diesel and that sorted it. I cleaned the fuel filter after about 500 miles as the bio cleans all of the crud out of your pipework. only reason i stopped using it was i moved and i have no local suppliers.
My 307 HDi has been using home made biodiesel for the last 4 years (about 30,000 miles). Had a couple of fuel filters in that time. I do have a problem currently on the high pressure side but the car has 140k on the clock so may not be bio related.
i always thought that to use vegetable oil in your engine the oil has to be used atleast once, like in a chip pan...obviously you will have to siv it to get rid of any debris - heard it mentioned this on top gear...i dont know if this is true, just what i heard.
but i also heard you can only use so much vegetable oil in your engine before customs start to take an unhealthy intrest in you and your vehicle...again its something i have heard...dont know how true this is...chopper may be able to confirm or call it bull.
I wouldn't use straight vegetable oil in an HDi. Well made biodiesel is ok though. I think Peugeot allow up to 30% but mine has run happily enough on 100% bio for 4 years. You risk compromising any warranty on higher blends of course.