We have 2 of the medium 7.5 kg Safefill bottles in ours, Had them for just over four years. They take the same fitment as the Calor Lite bottles they replaced as we were having a nightmare swapping them as Calor were trying to phase them out.
We fill up at our local Morrisons with no trouble. Last full fill up of a bottle there was just under £8
We some times top a bottle up if we are abroad as there are a lot more petrol stations that have them. You will need a different adaptor for abroad.
We were lucky as when we bought ours the company was in the 20% off promotion that eBay were running at the time.