Sadly, the flavour of almost all chocolate products went south a few years ago, and you'll now quite often see the phrase "chocolate flavour" on packaging. Anyone who liked the old Kit Kats (etc etc) discovered a while back that they had turned very odd, and that's because accountants overrule the taste testers.
Re Jaffa Cakes, they're not a biscuit, as there's no firm base. And no, they also don't taste so good these days. BUT --- as someone said, they ARE in M&S, and I recall a Raspberry version, as well as Lime and the trad ones (NO idea if M&S would have all options, likely depends on your particular branch?). I also think Aldi do them, their own 'brand', and though we don't go there very often (bit of a trek), they had seemed acceptable?
For those who haven't been keeping up (?!), cocoa prices rocketed up a few years ago, with the growers affected by climate change, and a major disease outbreak affecting the crops. Hence we now often get a chemical concoction as "chocolate Flavour" -- though it may well not be the same flavour you really liked?! I used to be able to decimate a packet of Choc Digestives (pref Plain), but now just one or two is quite enough. Maybe it's a sign the Good Lord DOES move in mysterious ways, the factors affecting cocoa crops having been delivered to aid my need to cut down on naughty foodstuffs?!
Oh, and Google also says:- A further cause is "Shrinkflation": In the UK, many popular chocolate brands have opted to shrink package sizes and adjust ingredients while simultaneously raising prices to protect their profit margins. Somebody with a degree must have written that -- one in stating the b* obvious?!!