It might be worth contacting the owner of the family tree, and see if they have any information they kindly wouldn't mind sharing with you. Where do you believe Peter was born, from the census information? It may be that that parish's records aren't online for viewing yet. You could try freereg.org, findmypast, or Sussex opc, as I looked on family search for you and couldn't find anything. If you know Peter's birthplace, search on the census just a 'Payne' and a birth range near his, which may come up with possible siblings or relatives. I believe that Eliza Oram may be a very distant cousin of mine, if my scribbled research notes from a couple of years back are correct!