In Britain, we also use the forms described by Certainly, but it's also very common, in the context of maths and statistics, to say 'nought' for the digit 0. So, in your examples, we'd have:
'nought point nought three three',
'nought point nought nought three',
'nought point nought seven percent'.
In all these cases, the first nought (to the left of the decimal point) is optional, but is often included for clarity.