The regular fuel filter is a big-ish one about two inches in diameter and three inches tall, installed in its own housing conveniently at the front of the engine. Easy to get to, and change.
The tank isn't that readily available new- the car's now 15 years old and I suspect a new one would be extortionately expensive, if one could be found.
For the refueling I've found a little pump that could be used for both re-fueling the car and for pumping used oil through a set of filters.
In the longer term the used oil would make it all much more attractive.
I'd thoguht of the Chinese (and Indian) restaurants but one said they cook everything in their oil- vegetables, fish, porks, etc.; and I've been lead to believe that oil used to fry meat should be avoided- so a Chip shop with seperate vats for the chips and fish would be ideal.
We'll see how it goes. When winter comes I may have to revert to a mix again or straight Diesel. Depends how cold it gets. Or I could get a conversion kit with heated fuel lines, a heating element for the fuel tank, a heated filter and adapted injectors and glow plugs. Its a little expensive, but if the oil is free otherwise....