Called to our local Jollyes Pet Superstores yesterday for some kitten food, and they have Royal Canin Kitten/Cat food on half price for the 2kg bags.
I paid £7.60/2kg bag which are usually £15.20.
The 4kg bags were still £25, and the 400g pouches weren't on offer, so were still (roughly) £3.99 each.
So the 2kg bags were great value.
Not sure of an end date for this offer, and hopefully it is nationwide, too - though it isn't mentioned online.
Hope this helps!