Silentnight single quilted mattress protector; machine washable and a decent thickness too. Great for using on a kids bed or in a spare room. Currently selling on Amazon for £8.99.
I found this upstairs in the electrical department where there is a bay of reduced to clear items at the end of an aisle. No price on the product or on the shelf but scanned at £2.50. Don't know if this is nationwide or store specific.