Train from London Kings Cross to Newcastle

Here is the Man in Seat 61's Guide to Train Travel in the UK. Maybe he can help:
https://www.seat61.com/train-travel-in-britain.htm

Lumo is an open access operator on the East Coast Mainline. Owned by First Group who also operate the GWR among others.

Not fancy.

Grand Central railway, another open access operator serves Sunderland and goes all the way to Kings Cross, or you can connect off LNER in York or Newcastle upon Tyne (get the name right, there are 2 Newcastles.)

Thank you Nigel -

Sorry I’m stuck now. There are 2 Newcastles? Isn’t one of them the airport?

My end destination is Seaburn.

I will be going from Newcastle to Sunderland and on to Seaburn. I might be getting picked up at the train station by a friend or I might need to get the subway (is that the same thing as metro??) to Sunderland and Seaburn.

Which train station name do I select?

You want 'Newcastle '. You can book a through ticket to Sunderlans via Newcastle, or the Grand Central direct to Sunderland.
The Newcastle to Sunderland train is run by Northern Rail, and runs non stop through Seaburn station.
Or travel to Newcastle, then take a Tyne and Wear Metro train from Newcastle Central to Seaburn.
The Tyne and Wear Metro is more light rail than subway, but subway will do.

It is not part of National Rail.

At Newcastle Central go through the ticket barriers, bear right and you will! see the entrance to the metro, before the station pub, on your left. Buy a ticket at the machines then go through the barriers.
Ensure you board a South Hylton train, not a South Shields train.

If you caught Grand Central to Sunderland you could continue on the Metro from there to Seaburn (same platform).

Yes you can buy from Lumo. They are cheaper for good reason. They have a strict baggage policy and very few trains, which are short 5 car trains. If one breaks down you have a long wait for the next one as they have no reciprocal arrangements with LNER. LNER run every half hour, so are the sensible choice.

Also LNER do 20% off advance fares for groups of 3 to 9 with no need for a railcard, so that may be the better option. The discount is automatically applied when you select 3 or more people.

Sorry I’m stuck now. There are 2 Newcastles? Isn’t one of them the airport?

I suspect what Nigel was referring to is that there is also a town called Newcastle Under Lyme in the north of the Midlands. But it is nowhere near Newcastle upon Tyne, and “Newcastle” is generally understood to mean N-u-Tyne.

But Newcastle under Lyme has had no station since 1964. In the list of stations to choose between on any rail booking site you only have Newcastle or Newcastle Airport.

There are various other places which have Newcastle in their name, especially in Wales, but none have current railway stations.

You can book to Newcastle Airport, but you connect on the Metro- it has no main line trains.

By the way you can't pay by contactless on the Tyne and Wear Metro. You can buy a Pop Card for free (like an Oyster Card in London) and get lower fares. But for a one time visitor it isn't worth the effort, and you can't get unused credit back. That is a product aimed at local commuters.

Thank you everyone for all of the help. I’ve managed to successfully get the tickets I need.