I don’t know if it has changed but at one time Calor wouldn’t thank you for returning the empty bottles, they had an airfield full of the blooming things! There was a recall on the lightweight 6kg cylinders, about 30 thousand were affected, and they had nowhere to store the defective ones. Of course if you were exchanging them for a refill then they were obliged to have them back but were quite content if they ‘vanished’ somewhere instead. Scrappys wont take them, our local one doesn’t even take the small Sodastream cylinders either.
Pete.