A dialect combines vocabulary, grammar and accent. I was using RP in a loose sense, meaning UKSE spoken in RP.
This video explains the difference between a language and a dialect:
As you can see, Jozi, as a variety of Afrikaans is a dialect, even if it is looked upon with prestige.
Bundjalung is a language, and I would, after serious consideration, consider the "Serious Knowledge" variety that Tim was talking about as a non-literate equivalent to a written language's written form.