Not sure if national, but local (Royston, Herts) Tesco is giving away free limited edition Whiskas cat bowls with purchases over £6 of Whiskas products.
The bowls are in a big Whiskas promotional display that clearly states "Free bowl when spending over £6 on any Whiskas product" - so I purchased 2 packs of 12 tins for £6.50 each - but when you scan the "free" bowls through they scan at £4.99.
I went to customer services to have this rectified and was told that the promotion is only on pouches and dried food sacks (which IS detailed in a tiny shelf label stuck to the bottom of the display so you won't notice it!) Argued the toss and told them the Whiskas display stand quite clearly states in big letters "Any Whiskas product" and they agreed to refund the £4.99 per bowl that had scanned - argued a little more and was given the double the difference too (although did have to speak to a manager to get it).
UPDATE: 28th September:
Looks like the potential for free bowls against ANY Whiskas product is off - certainly in my local store (Royston, Herts) where they've now stuck labels over the display stand specifying it only applies to Whiskas 2kg dry food or the 12 pack pouches.
Still a deal for free bowls though if you regularly buy either of those specific products, and other stores may not have changed the signage yet - so the "ANY product" deal might still be had elsewhere.