I am not quite sure what you mean by a refund. You mentioned accommodation so I assume you are either cabin crew, travel abroad a lot or staying at friends.
Presumably you will be going home either the same day you go to work or within the month so will buy open returns, why you would need a refund? However, if you really do you want to refund the ticket you have bought then you can do, although there is a £10 administrative fee.
Your best bet is probably a season ticket. Alternatively if you won't be going for many days in the week, day returns from Tonbridge are best. You will most likely have to buy these online though from the sounds of it if if the machine do not offer your discount
I know how you feel, it can be a rush to change trains at Redhill which is why I suggested changing at East Croydon or Clapham Junction onto the same train that you would have gotten on at Redhill. You could even board it London Bridge or London Victoria although facing central London is probably the last thing on your mind after work lol.