You must pay HMRC duty on vegetable oil when you put it into your tank. There is no allowance for VEG.
ONLY biodiesel is exempt of DUTY and VAT (up to 2500 litres per calender year) if you make it yourself.
If you get dipped with veg, you could be in trouble
If I was to run VEG, in addition to filtering I would also heat it up and leave it to settle for a few days, drain off the bottom water and crud.
Then add 5% petrol in summer more in winter.
Don't forget to add an inline filter as the veg will clean out the fuel tank and lines of rubbish. I put mine just before the main fuel filter
I bought 10 plastic ones on ebay for £1 each