My astra is a P.O.S. with 140k on the clock, I personally wouldn't want to try it in my newer common rail diesel without some research try some car forums. A mechanic i work with recons he's seen plenty of failures on the bio diesel, if you go down that route make sure its filtered well and still mix it. I personally use neat veg, and mix, not encountered a problem and have been caught out in the cold snaps and it still works. I think the main thing is don't be greedy and you'll be fine. Please excuse my english as i'm 3/4 thro my second bottle of vino !
p.s be prepared for a smell when you run your car on it, more noticable at traffic lights