Just been in Tesco at Great Yarmouth, their 2 litre bottles of oil are on sale at £5 for semi synthetic and £6 for fully synthetic. They had a variety of viscosities and specs. Presumably the sale is available at all their stores.
I know from the numerous discussions that oil quality and brands is an emotive subject, but it's a good deal for anyone who is happy to use it or to top up with it.