6 for £27.99 is a third party seller the other two prices are from Amazon UK. Really have to be vigilant on Amazon, it's a minefield of tat and foreign based sellers.
Also lookout now for anything sold by "Amazon EU", because that will of course attract import duty and then VAT on the whole lot including shipping. I've found it pointless to order stuff from the EU lately. Ordering from the USA is generally cheaper overall and theres usually a better selection.