Thank you both.
I have checked the 1911 Census and found a Marianna Carter at 5 Brintons Road, Southampton. James and Marianna married in 1909 and were both in their 40s. Her lodger was born in Barnstable (near my ancestors).
I may well be chasing non-existent connections here. My granddad, Edwin Frederick Ball, was born (1881) and brought up in Tavistock Workhouse. He always said that he lost 'a brother' on the Titanic. I found W Ball on the crew list, also known as James Carter, and the remote possibility of some link intrigues me.
I know that many people at that time claimed links with the Titanic, presumably for a variety of reasons, so this is probably a fruitless search. I found a man called John Poole Penrose who came from from granddad's family's village of Mary Tavy, near Tavistock. He also died on the Titanic.
I'm clutching at straws, maybe, to find a connection that doesn't exist. But I do like a good mystery!
Any further thoughts, particularly how someone could sign on under an alias but finally be identified under his 'real'?? name, gratefully received.