I am a dual British and Australian citizen. I am British by descent and I have applied for my passport but it hasn't arrived yet and am worried it won't in time. I'm going to be staying in England for 6 months so I'd need a visa if I wasn't a British citizen. As I said though, I don't have my British passport. Does anyone know what to do in this situation? Could I enter with my Australian passport?
Have you already received some official confirmation of your British citizenship? If so, you can probably enter with that, possibly in combination with your Australian passport.
If you do not yet have official confirmation of your British citizenship, you have two options:
Enter on your Australian passport and hope that the official determination on your British citizenship comes through before you leave, or before you have some other need to prove your right of abode. This will invalidate the 6-month limit placed on your visit.
Travel to the UK using your Australian passport, but at the border present your evidence of British citizenship. The border official should let you in without any time limit.
The basic principle is that as a British citizen with right of abode, you can stay as long as you want. The only reason you'd need a visa would be if there is some question about whether you in fact have right of abode in the UK.