Originally Posted by McClane 
Says on the Orange website "As well as separate numbers you'll get separate bills". So looks like this could be the answer
When I had Line 2 I got two separate bills, but they were printed as part of the same statement and were billed as part of the same account. So it was a faff for me since I had to put it through as a cash expense rather than get it paid directly, but sounds like it's fine for you. The Line 2 service itself works really well, apart from the roaming. I always used to like the way they filled in the spools on the 'tape' icon to tell you which line you had voicemail on.