Unfortunately, one can't buy Lucky Charms in the UK supermarkets any longer, but, fortunately, for a price, one can still buy the genuine imported (USA) product. Three 326g boxes for £12.65 seems like the best deal. It might be a bit more economical to track down some tri-pack deal on 453g boxes (which do exist), but then you'll just eat more of the cereal and it'll cost you more in the long run (but if you have the money -go for it!).
This is a classic cereal -the very first 'kids' cereal created back in the early 50s- which is still great, and unmatched to this day, except by a couple of other American cereals. If you've never tried Lucky Charms, buy a box and discover why even adults love them! If you put sugar on your cereal, I think you'll like this product (like all these cereals, they were created by General Mills -Nestlé had absolutely nothing to do with their creation -they just distribute them over here). Basically, Lucky Charms is Cheerios (original) with marshmallow bits.