Where can i get cheap train tickets to London?
From Sheffield it depends which service you use. Cheapest would be the London midland services. Best thing to do is pop into your local station and ask the clerk, they have all the information on hand and can check pretty quickly for the time and day you want to travel there and back, they should know all the routes and restrictions and get you the best deal, make sure you go in as quickly as possible, preferably up to 6 weeks in advance for the best ticket price. Good Luck, its a lot better than trying to find it on your PC or asking a voice on the telephone.