I have never split crumpets to toast them. I just toast them whole and put the butter on top.
I might split and toast muffins though.
NOTE: That does NOT mean American muffins, which I would call cakes - like cup cakes but without the heap of fat, sugar and artificial colouring piled on top.
Small cup cakes with much less of the fat/sugar mixture would be 'fairy cakes', or with just simple icing or maybe containing dried fruit they would be what my grandmother called 'buns'.
Confusion on confusion. To me a bun is made with yeast and like a very small loaf of bread (with currants in).
And then there are scotch pancakes, and pikelets, and we are coming back to crumpet territory.