Rail Ninja are scammers. So if they haven't yet delivered anything you need to reverse your CC charges now, and then forget you ever heard about them.
You do not need to book train tickets "way in advance". Trains would be useless if that was required. Train travel is mass transit. How far in advance do you book the NY subway? How far in advance do you make appointments are your grocery store?
Trains are used by people to go about their daily business. That is not possible if you need to book months in advance.
Book train tickets with the actual operator. And yes, you can do good deals if you book in advance, but there is no need to book half a year in advance. If you were to rock up to the station in London right now and say "I want a ticket for the next train to Edinburgh" you would get one. But you would pay a high price. Booking a few days before already gets you significant savings, and booking a few weeks in advance even more.
There is no need to book half a year in advance, and there is no need to go through third parties.