How do I change rail services when travelling on two different services?

I'm going to see my boyfriend, and have just realised that I need to change rail service (like, for example, I need to change from London Underground to Chiltern Rail). How do I do this? Do I buy a ticket before or after I get on the train? Do I have to buy a ticket from the change-over station?

Use http://www.thetrainline.com to buy your tickets in advance to save money and to get all the changes and tube tickets you need.

If you are starting your journey on the Underground, you will need to buy a ticket for that journey (or use your Oyster Card) and buy a seperate ticket on Chiltern Rail. If, however, you are starting your journey of a service other than the Underground you buy a through ticket from A to B which witll be valid for the Underground. For example, I had to travel the other week from where I live in Sussex to Durham. I got one ticket which covered me for the Southern Trains part of the journey, the cross London by tube from London Bridge to Kings Cross and the journey from there to Durham.

Just Buy a ticket from your starting destination and say to the ticket office personnel, can i have a return ticket from xxxx (Starting Destination) to xxxx (Finishing Destination)

Firstly, does the journey take place wholly within the London "zones"? If so, you may be able to do the entire journey on an Oyster card - check the TfL website.

If not, but you live in London and you already have an Oyster card for the Underground, you'll probably find it cheapest and easiest just to buy a ticket for the Chiltern service once you get to that station.

While it is possible to buy one ticket to cover any possible train journey within Britain (including changes involving Underground travel or other local city services), I don't think you'd be able to buy such a ticket from a London Underground station. You'd have to buy it from a main line rail station.

ok if this is a underground to mainline yes you need separate tickets but if its between to mainline trains of the same or different 9 times out of 10 you wont need a second one however when you look make sure your route is straight forward and you not going backwards on yourself some routes may require a second ticket but the websites will tell you that if you want help
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