you are allowed 2500 ltrs of wvo, svo, home produced biodiesel, in any form for private use, this has been covered in various forums since it first became the norm, If you take a bottle of veg oil from the shelf, remove the top, and pour it into your tank, you are producing svo for use in a diesel engine, there has been reams of forum disscusions on this subject, including hmrc, the only things you are not allowed to use are rebated carbon based oils of any kind