Interesting fred.
As some of you know i was running the ol veg oil all summer in me 19J...yes yes i know the fuel pump isn't upto scratch for this kind of thing, but she did it without fault until the cold weather came in.
Anyway after learning abit about it all, i'm going for the twin tank set up ready for a 200Tdi to drop in, a small 10-15ltr homemade tank under the seat will fit for start up and getting engine to temp, then switching over to 100% veg oil afterwards and switching back before journeys end.
I can get hold of used oil as much as i like and found the difflock forums relating to this kind of thing very useful.