Heathrow to York

Is the train station easy to find from the tube?

The tube station is underneath Kings Cross train station. You just follow the signs.

I'll let others discuss ticketing but I did a mock booking and got offered off peak tickets both ways.

I'm looking at tickets for today, and looking at 0715.

There are Advance Tickets (cheap train specific) available on all trains after 0730. That is normal.
So it is actually impossible to pay full fare.
Before the 0906 train they are peak fares. So I would kill time and get a train after 9am.
In any event on a weekday the 2T is not valid until 0930.
On such trains the full fare is a £75 Super Off Peak Single, before railcard discount. Valid on any train.

So my advice is that after you have cleared immigration, do two things in order-
Check the Piccadilly line has no problems, and be willing to reroute onto the Elizabeth Line if needbe.
Then get on to the internet on data or wifi and buy Advance Tickets for not less than 90 minutes time. Yes you can get them at KC but why wait?
If perchance there is an event on that day and Advances are sold out buy the £75 ticket (£49.90 with railcard).
On the way back buy Advances ASAP, like today.
There is actually a travel hack to that.
The cheapest by some margin, if slower, route is often into St Pancras, changing at Sheffield. Buy it as York to Sheffield, and Sheffield to St Pancras.

Jules, I would suggest the LNER direct route from Kings Cross, even if it is a bit more expensive than the St. Pancras train. You will undoubtedly be jet lagged, and it will be much easier to rest on a direct 2 hour train ride, than having to get off in Sheffield to transfer to another line. You could always take advantage of it on the way back if you wanted to save some money.

Then get on to the internet on data or wifi and buy Advance Tickets for not less than 90 minutes time. Yes you can get them at KC but why wait?

I agree. You could even get online while you're on the tube to Kings Cross and order them then.

Great help!

When we leave York, our destination is Premier Inn Westminster bridge waterloo. Should I still purchase York to Kings Cross, or is there a better station for me?

Does the Two Together Card need to be purchased prior to sale of ticket or just prior to travel? I just went thru the booking process up to payment and it never asks for a card number. Of course, I would eventually buy one, but it appears easier to buy it in person. Also, its valid for a year, so I'd love to wait as long as possible in case we choose to come back within a year.

Also, just looking at a ticket for York to Kings Cross, what does the statement in the quote marks mean?! Are they saying the time can be changed prior to travel? If so, they probably would charge the current rate at the time of change?

Restriction code: GC
View restriction details
Fare category: restricted

"Advance tickets are valid only on the specific booked train but can be changed before departure of the first reserved service."

Should I still purchase York to Kings Cross, or is there a better
station for me?

You don't have a choice. Trains from York arrive at King's Cross.

You can buy the railcard any time before travel.
Most people here prefer a digital card, personally I prefer a real paper one. All personal preference.
I got my current paper one by buying on line and specifying it be mailed to me, probably not an option to you.
What you don't want to be doing is buying it at Kings Cross on arrival day when jetlagged. That is a recipe for errors.
You certainly don't need it in hand when you buy the ticket.
As I said it depends how keen you are to save money. But you do have a choice of station- you could return to St Pancras if you follow my via Sheffield option.
Another often used way to save money from York to London is to travel to Kings Cross via Leeds. Book an advance York to Leeds and another Leeds to Kings Cross, changing trains at Leeds.
York to Leeds advances go on sale 8 weeks before travel.
it all depends how cheap you want to be.
If you wanted to you could buy an Advance Ticket York to London Waterloo - that would include your Cross London tube fare from KC to Waterloo. BUT it would have to be collected at York as a paper ticket. TfL can't accept electronic tickets. Possibly not worth the effort.

Thank you, everyone. Just purchased my York to London ticket on LNER. I do have an app, but I did it thru the website. I made an account which gives you a 5GBP discount, further, this is such an easy website to use and my credit card processed immediately. I guess it helps that it is in English! ;)

It was purchased almost 3 months in advance and was 24 pounds for 2 people. That's a bargain in my mind.

The ticket is stored in the app so that is very easy!

I've set up a calendar reminder to purchase the two together card online a couple days before our trip.

Without digging in very deep into the Fares Manual Fare code GC probably means you can exchange the ticket before travel by paying a £10 fee and excessing the ticket up to the then cheapest ticket.
If anyone has ready access to the current NFM it will be @Marco. Personally I think you'd need to buy a whole new ticket. That would probably be easier anyway.

York seems to be an intermediate stop for LNER trains from Kings Cross to Edinburgh. Make sure someone is awake so that you get off at the proper stop. Maybe set an alarm on your phone for X minutes prior to your scheduled arrival.

Have a great trip!

Thank you, isn31c.
Good point, Rocket

Restriction code GC: https://www.nationalrail.co.uk/ticket-types/validity/gc/

Outward Travel
Valid on London North Eastern Railway (TOC Code: GR) and connecting services.

Seat reservations are compulsory.

So nothing of any real significance.

GC is a bad choice of name really as it could be confused with Grand Central. But they have both been around for years.