Coke was the original “smokeless fuel” coal which was processed so it gave heat but little smoke when burned. It was acceptable to burn it in “smokeless zones” where burning coal, which generates a lot of smoke, was prohibited.
You’ve heard what nutty slack was- there was also “gassy slack” poor quality broken coal that smoked and smelled (at least it was called that in my area, which has lots of mines)
My granny used to say “Venus on a rock bun”
She would also express surprise with “yee gods and little fishes”
“All my eye and Fanny Martin” was her way of saying someone was “spinning a yarn” ie making things up based on very little truth,
“sixpence short of a shilling” for someone foolish, lacking common sense (there were twelve pennies in a shilling in old money)
And “bent as a ninebob note” (a shilling was a “bob” in pre decimal currency. In the old-money half a £, ie 50p was a ten shilling note, there wasn’t a nine shilling note)