I've always known it as 'scone as in throne' however if I'm with my dad's side of the family it's 'scone as in gone'. The amount of arguments the pronunciation of this has caused (and probably will cause)...
Wonder if it varies depending on where you are from? I'm from the north east, and to be fair I've never got onto the subject really. My mam says scon too though.
Tend to say 'scon' Cant use "had to change spelling" as justification; gone, none, done (I pronounce 'dun') It's "Castle" that causes all the issue where I am... silly southerners and their make-believe 'Rs'