What does British English sound like to Australian speaker?

Scottish English? My Scottish personal trainer reports people have difficulty understanding her. I can’t fathom why, and I don’t, but maybe my ear isn’t as tin as I think it is. (FWIW, it’s rare that any Scots creeps in to her speech: cannae only once in a while.)

Northern English? I think highly of it, and I think most Australians do; Freddie Flintoff is an honorary Australian, and the accent hasn’t hurt that.

As OP makes explicit in comments, what he’s actually asking about is Received Pronunciation.

Well, Cultivated Australian used to be the dialect of the Australian elite, and Cultivated Australian was not terribly different from RP. (The main difference was the plural: boxes [boksəz] vs [boksɪz].) If you watch Australian TV shows from the 70s, you’ll notice that all the lawyers and doctors talk like Poms.

Cultivated Australian is still around, but it’s been stigmatised through resurgent Australian nationalism, and no Australian politician will touch it now.

(The last one I remember speaking it is Alexander Downer, of a three-generation political dynasty, now High Commissioner to London like his father before him—and not taken terribly seriously by many Australians. His daughter Georgina is angling for a seat in parliament, and doing radio to get her brand out. And she’s as Ocker-sounding as the rest of our contemporary politicians. Any elocution lessons she’s had are carefully concealed.)

So. If a jumped up local imitation of RP is stigmatised, how do you think actual bona fide RP fares?

Yeah. Suspicion and derision. All the old resentments against Mother England are still there; all the old admiration of Mother England isn’t.