Have established that there is fuel at the injectors. It's looking like it could be a bad batch of bio that I put in yesterday. 
Open the tank from the boot floor or take off the filler neck pipe, will be the easiest way, or if your using a pump then simply attach pump to fuel line in engine bay...
Thanks Jon. Would that be through the inspection panel in the boot floor? I've never looked under there before, but can I get access to the tank through there? Also, (sorry for all the dumb questions), where do I get access to the filler neck pipe?
Yeah through the boot floor, 6 screws hold in access panel and then a few more hold in sender unit, lift that out the way and syphon from there. If you look under the body where the filler cap is you will see the pipe going from the filler hole into the tank, it goes through the chassis leg I believe, there should be a section of pipe held on my 2 jubilee clips, undo these and it will give you good access again but be warned, it will come gushing out when you release the clips...
had the exact same symptoms on a sherpa van years ago with the prima engine,turned out to be(after searching for days) the tiniest of splits in the fuel line pulling in air causing all the issues,not saying its the problem in your case but i would rule it out
Just dump the bio in as it is with some proper derv 50/50 or something like that to dilute and it should be alright
Cant see it being any worse than using straight veg mixed with derv like I do
this comes from the man that is now questioning if the petrol in his non starting V8 is actually combustible or not?
hmmm..............................