Ask, then believe the answer
Goat is available to order at the counter only in the sense that you ask, and the butcher tells you whether he can get it. It is not a tray you should expect to see every day, and this page is not a promise that it's in. If it isn't, he'll say so. Mutton, which is the older sheep, is what we do sell for that long, deep curry.
Why the word causes arguments
In a Glasgow butcher, mutton is sheep over a year old: darker and firmer than lamb, and labelled so you can tell. In many South Asian kitchens the same English word means goat. Both are halal animals. They are not the same taste. Goat is leaner. It still wants a low flame and a lid, and it still punishes a rush. If your auntie's recipe says mutton and she means the goat she grew up with, say goat when you get to the counter.
If he can get it
Treat it the way you'd treat a stubborn pot of mutton. Brown it properly, then a gentle simmer, covered, until a piece gives up. Don't add the potatoes at the start. And don't plan the dinner around goat until you've asked. Lamb shoulder will still make the karahi if the answer is not today.
Goat, plainly
Do you sell goat?
Ask at the counter. We don't promise it on the day. Our mutton is sheep.
Is your mutton goat?
No. Mutton here is sheep. We label which is which.
Do you deliver goat?
No. We don't deliver anything. If we can get goat, you collect it from Shawlands.
We're at 44 Kilmarnock Road, Shawlands, Glasgow G41 3NH. Opening hours and the map.