In the UK, lamb is pretty much an everyday meat (well - every week...) but goat is regarded as pretty exotic - common mainly in Afro-caribbean takeaways or restaurants. (I'm from the South-East so this might not be true in other regions).
Mutton - I don't recall seeing very often at all in butcher shops. As the meat in takeway - it's more common but sometimes the terminology isn't precise. Some Indian takeaways use the word "meat" when they mean something sheep-based. And "mutton" sometimes means "goat" (and vice-versa). And "mutton" sometimes is just lamb...
Same in South Africa...."mutton" usually refers to lamb. almost no one has a "lamb curry" or "lamb bunny" (Google it). It's "mutton curry" or a "mutton bunny".
Mutton - I don't recall seeing very often at all in butcher shops. As the meat in takeway - it's more common but sometimes the terminology isn't precise. Some Indian takeaways use the word "meat" when they mean something sheep-based. And "mutton" sometimes means "goat" (and vice-versa). And "mutton" sometimes is just lamb...