HELP- the blur of student finance

So I'm looking to study at Business Management in September, had all my offers etc etc.

However, i'm looking to sort student finance. I'm in the position of living with one parent and their partner who isn't legally a career of mine (they're not married). Does both incomes have to be declared when looking at means tested student finance? I know that in some places on the government website it says 'parents income' and in some 'household income' so this had led to come confusion, as I want to abide with the law obviously. This will make a huge difference between the amount of money I will receive when I'm away from home studying my course (around 3k) .
I'm sure someone has been in the exact same position as m, or if anyone knows more than I do then please help!