I have seen these, as I'm sure you have, fitted to steel tanks, and they just seemed to be an extension of the filler in 2" steel pipework, capped at the fill end. I don't know how they would be fitted to a plastic tank, but I guess it's possible.
However regs have rightly tightened up. At a guess (as I can't see any offered for sale) and at the very least you would need a mini-bund at the fillup end to catch spills, and some device to auto-stop the fillup if the tank is full.
They have remote fillers at commercial premises. Why not give your oil supplier a call and ask to talk to their tank installer, or talk to an installer directly?