Okay, so we a both coming at this from two points. I accept your point, but also still think the cylinders are within the law (especially when purchased, not that long ago). Certainly, more legal than re-filling Non-refillable. I've heard some stories of people tilting the large cylinders upside down and refilling the small ones using a 'special adaptor'!!!
However as I am not prepared to put anyone at risk, I am withdrawing the cylinders from sale. It was exactly this problem with LPG supplies not letting me fill at garages, why I decided to go down the route of 'gas-it' and an external filler in the side of my van.