All of your answers were on a programme called 'Black Market Britain' or something similar the other night (might even have been last night come to think of it)
Getting the dye out of diesel (fuel laundering as it is termed) and using kerosine based heating oil is costing C&E a fortune. They are beginning to carry out roadside checks different places. One guy interviewed had a job getting rid of the old fuel from cars about to be scraped. He reckoned 20% of the tank he emptied were running on illegal fuel. Apparently in N.Ireland 2/3 of the garages are selling illegal fuel and the legit ones are almost all going under - according to the programme anyway.
Was worth watching. Apparently the fuel laundering industry is worth a fortune. And in N.Ireland where there is easy access to cheaper fuel from Southern Ireland (less tax) it is pouring into mainland Uk and N.Ireland big time. Big time links to the IRA apparently.