The product Fox Chocolate 3 Finger is most likely a popular biscuit/cookie product from the British brand Fox's Biscuits, which offers several "finger" style chocolate biscuits.
Since Fox's is primarily a biscuit company, the product is not a solid chocolate bar, but a chocolate-covered biscuit.
The search results show two main "finger" products from Fox's:
Fox's Chocolate Fingers (Also simply "Chocolate Fingers"): These are thin, rectangular biscuits fully coated in milk chocolate. They usually come in a multipack or carton, and are similar to a brand like Cadbury Fingers.
Note: These are typically thin, single biscuits, and the packaging doesn't usually specify them as "3-finger." A common portion size may be three biscuits.
Fox's Viennese Milk Chocolate Dipped Fingers: These are short, buttery Viennese biscuits that are often half-dipped or fully coated in milk chocolate.
Note: These are also sold as individual biscuits within a tray/pack and are not typically joined in a 3-finger configuration like a wafer bar.