I could only speculate on the economic realities in the UK. I have certainly noticed that services considered common in some places, are very expensive in other places which are less well traveled. A bigger customer base seems to encourage competition, greater infrastructure, and lower prices. Other times, it's just the cost to get it there for you to buy. When I bought drummed Avgas in the Canadian arctic, it was four times the price as it was at an airport 250 miles away, but I knew that going in, had zero choice, and paid happily. It was my choice to fly there.
It's just the way it is.....