Hotel by Heathrow

Which airlines? There are four terminals. Each with hotels located either in the terminal or nearby.

Hands down, no contest, the best hotel at Heathrow is Sofitel. When I became sick there they took such amazing care of me, bringing in doctors, specially prepared foods, etc,It remains my favorite hotel!!

30 days + out, Heathrow Express from Paddington to LHR is 10 GBP per person, and
gets you there in 15-20 minutes.

So you can conceivably stay in downtown London, either using Heathrow Express
or the Elizabeth Line, which is about the same price. Elizabeth Line gives you a
couple of more options for hotels since there are a few stops in London, but there
are lots of hotels around Paddington.

I think the 3 hour rule is subject to a) whether you're checking bags or not b) how
familiar you are with the airport c) class of service (business class obviously less
line/hassles than economy).

Since you will be leaving the airport secure area, you will need a UK ETA.

I am not very familiar with Heathrow Airport. I have been there once. I will be flying on Alaska Airlines back to SEA. New LHR flights on Alaska Airlines started! I have no idea what part of the airport they will be situated. I will be applying for the UK ETA soon.

Should you decide on a Heathrow hotel instead of (my preference) one in London, then FYI, Alaska flies out of Terminal 3. Definitely want to be at the airport 3 hours before departure.

Here are three different threads that were posted in the last year or so showing recommendations for hotels near Terminal 3, which is where you will be leaving from:

https://community.ricksteves.com/travel-forum/england/london-heathrow-departure-hotel-for-delta-flight
https://community.ricksteves.com/travel-forum/england/heathrow-hotel
https://community.ricksteves.com/travel-forum/england/heathrow-airport-hotel-5e11e0cc-722f-43e5-9f4a-e213a4f617e4

Since you will be leaving so late the next day, you might want to consider traveling to Windsor to see Windsor Castle and the surrounding area. It is not that far from Heathrow, and it is easy to get there from the airport. https://community.ricksteves.com/travel-forum/england/heathrow-to-windsor-f3ffba50-5f12-4b1c-9ad5-c6142fa784df

I have a similar question, but it looks like my departing flight on British Airways (to JFK) will be at LHR Terminal 5. My ticket doesn't specifically say which terminal; I guess you have to wait for your boarding pass to find out for sure. However, I Googled it and learned that " BA’s main base is Terminal 5A at Heathrow. Some BA-operated and codeshare flights depart from Terminal 3. Always confirm your terminal on your boarding pass or in the BA app before you travel." https://www.thepointsanalyst.com/british-airways-heathrow-terminal-5/

I need to check in about 9:30 in the morning, so I don't have to be up before dawn, but I'd like to sleep somewhere near enough that morning traffic won't be a major source of stress. Are the Bath Road hotels still appropriate for my needs?

BA flights from Heathrow to JFK depart from Terminal 5. (I've taken plenty of them).

Don't think of 5A, 5B, 5C for getting to the terminal. It's just Terminal 5. B & C are separate satellite buildings you get to by lower level tram from the main terminal building (5A). However, all flights to the US depart from B or C.

The easiest and closest hotel to Terminal 5 is the Sofitel. It is literally connected by inside walkway. But it's not cheap.

There are hotels at each terminal which can be reached by either a free ride on the Underground, Heathrow Express or Elizabeth Line.

Or you can pay to get to one of the hotels on Bath Road.