The premise for the "Bar of Plenty" is so simple, and so good, simply add more stuff into a chocolate bar. The do this because some people prefer to have lots of stuff in their chocolate, they like the nuts and crunchy bits a little more than they like the chocolate. The folks at Ben and Jerry's ice cream understand these kinds of people, and so do the people at Cadbury.
The thing about this kind of treat is you can easily mess it up. When you increase the number of things in your bar you have to make sure that the ingredients are still evenly dispersed. If I got this bar and all of my hazelnuts where crammed into one end of the bar and my crunchy bits on the other, it would ruin it completely. The Bar of Plenty doesn't do this at all, in fact it's one of the most evenly distributed chocolate bars I've ever eaten.
The other thing that can ruin a bar like this is lesser quality chocolate. When you have lots of nuts and sweet stuff in your bar, you want the chocolate to be a high quality to balance the flavour. Seeing as it's European Cadbury chocolate you can bet that the chocolate is spectacular. The flavour of the ingredients blended perfectly with the smooth chocolate.
With each bite of this bar evenly filled with an abundance of nuts and crunchy stuff, and a quality of chocolate that is top of the line, in candy bar terms this bar is truly spectacular.