Cadburys and other big manufacturer’s are just chocolate flavour confectionary, not really chocolate. A dairy milk bar is mainly milk and sugar. Not that there’s anything wrong with it but it’s not real chocolate. Same for all the other brands like Nestle.
Real chocolate, like real coffee, tends to be expensive. I like Willie’s Cacao, Hotel Chocolat, Cocoba, Artisan du Chocolat and other artisan chocolatiers I can’t remember having just visited their London stores. Still like a bit of crap and a Creme egg though, which always tasted more or less of sugar and not much more.