Presumably you'd take the train from London to (to where? Plymouth?) and then a ferry?
How long is the ferry journey? Is it possible to do the ferry journey overnight in a sleeper cabin - or too uncomfortable/expensive? How much total time (approximately) in transit?
Any details would be appreciated (such as where I might look at train and ferry schedules). I am inclined to think it would be a logistical challenge....but maybe someone has information that will make it seem easier!