What kind of advice do you need? To get train schedules, you may use any travel planner, e.g. https://www.nationalrail.co.uk.

But on the 25th / 26th there are no trains at all. It's christmas. First train from London to Edinburgh is in the morning of the 27th (7.06 from Kings Cross).

To get train schedules for the 28th, just use the travel planner mentioned. 

As @Hektor says, no trains at all on the 25th or 26th. There are coaches, see www.nationalexpress.com, and flights.

For Edinburgh-London, you can search train times and reserve a seat (strongly recommended!) on the LNER website https://www.lner.co.uk/travel-information/make-a-reservation/