I just discovered this at my local Morrisons in Killingworth. This deal wasn't advertised. There was a deal for 10 cans for £9 so we asked how much it was for the 20 cans. When the man scanned it through and it came up as £10 we decided to buy two crates. There was still one crate left on the shelf for any local cider drinkers. Not sure if this is national but not sure why it wouldn't be.
Ironically i don't even like cider, i bought it for a friend (seriously).