Ah, so this raises the perenial question of what it means to "live" <somewhere>. Could you borrow an address to tell them you "live" at? Or is the actual question "What is your postal address?" perhaps? (It might be different from where you sleep most nights.) What if you tell them you live on your boat in the Oxford area and move around? How would they know where you were on any given night?
Just questions for you to consider. No need to answer them here.
Another idea if you need more space on the boat is to get an additional boat. Then you could be living in two places at the same time!