Something for fly tipping stereotyped but maybe litter too is that “white van man” demographic so what about posters and roashows at Construction/Building associations but also maybe doing some engagement events at Jewsons / builders merchants to raise the profile of litter and FT and Waste Duty of Care ? These places are often on grotty industrial estates which being privately maintained dont get cleaned and you get alot of e.g. pallet wrap blowing off the lorries and such like so maybe their staff could engage in a pick and they might also donate you some building materials towards LP4N type projects or dumpy bags and tools to clear garden waste and litter