I think you're running the lucus pump aren't you?
be careful on those as I used some bio on mine and it didn't like it, but to be fair it wasn't filtered properly, something to note as well that you will need to change your fuel filter more often as it will clog up quite quickly,
don't worry about your fuel pipes as they are corrosion resistant, (pugs were used by farmers so they took biodiesel into account), the fuel filter housing is warmed on these engines from the coolant system, but if you upgrade to a bosch pump (a fairly easy and cheap affair) then you can run straight veg oil with no problems, just remember to add a thinner of some sort, but do note this is the bosch pump ONLY
in your situation though I would use a 50/50 mix with some good quality biodiesel and pump diesel
these engines do like biodiesel, it's just the lucas pump can be finicky,