you know whats it like you buy a single ticket on the train which costs a fortune as u wont be returning and then something happens and you need to return. The trouble is a single ticket and a return ticket can be almost the same price! so what do you do, well you could buy another single ticket which depending on the route could cost you a fortune but have you thought about asking the driver to add an excess on your ticket!? I'm not sure if this is allowed but it might be.
eg just say a journey costs you £40 for a single ticket and it may cost £44 return but you bought a single ticket. Well you could buy another £44 ticket or ask the guy to add the difference as an excess eg £4 to upgrade your ticket to a return.
if anyone has tried this let us know!