There have been After Eight Eggs - about three years ago.
In the 80s, there was a minty egg. I am not sure who made it but it could have been Cadburys.
Cadbury seems to make many products in the UK that we never get to buy. The Cherry Ripe is made here, then sent to Australia. I can't understand their reluctance to allow it on to the Uk market. The only reason I can think of is that the chocolate is different (to cope with Aussie weather) so perhaps they can't be bothered buggering about with Uk type coatings as well as Aussie coatings.