If the red diesel is being used as a "wholly and necessary" part of the business, it is a fully deductible item anyway (inc any VAT), but you still have to make enough money to buy it in the first place.
Our minimum delivery on to the farm is 1000 litres, so thats a fair amount of cash tied up each month until it's used up.
If you are thinking about the impact on the costs of food, consider that we sell prime lamb into the market at about £40 each. That will provide about 38 Kg of meat to the butcher. Our local supermarket delicatessen counter is selling that meat at up to £7 per Kg.
There seems to be continuing confusion on this subject; however I imagine that lower tax diesel (red diesel) will continue to be available to commercial users. I imagine that leisure users will simply be required to use white diesel. This will be enforced by tank dipping from time to time. Herein lies a problem because the red dye stays in a fuel system for while but I expect that this is not insurmountable. In practical terms it will be simple to police - the waterside suppliers will have no choice but to supply white diesel and unless the boat owner is prepared to jerry can red diesel to the boat (or arrange a frinedly tanker somewhere which is going to to obvious to the authorities and indeed the reputable tanker suppliers will be very nervous about supplying leisure boats with red) there will be no choice but to purchase white diesel. Job done.