Tomorrow (Friday) I've got to travel into Waterloo East from Headcorn with Southeastern. I've got a Z1-4 travelcard on my Oyster so I wanted to know if I can just buy a paper ticket for the bit of the journey from Headcorn to the Z4 boundary and then let my Oyster pick up the rest of the journey from that point and, if so, does anyone know which station I need to buy my ticket to?

A.