Discounts re-train tickets help.

I commute everyday exept weekends, Bighton to london bridge, I have
searched online
for ways of booking indirect, to save money. I have found the train
line . com, they are offering 35% discount
on monthly tickets, anyone know of this ?. Also I have been told of
money saving cashback . com with
similar discounts on train & coach travel.. any idea's...