London Heathrow to Central London

You say you're going to have luggage. Does that mean you'll be carrying suitcases or are you talking about traveling with 21" rolling carry on bags?

If you're using rolling bags, I suggest taking the Heathrow Express' 15 minute train ride to Paddington Station. Go up the escalator and hail a cab for a short ride to Coram St.

If you are traveling heavily, a taxi all the way might be your best way.

We usually stay along the north end of Hyde Park so the Heathrow Express works out the best for us.

We will have the larger 24" checked bag. 1 bag each person.
Thanks for the advice.
The Holiday Inn appears to be close to Russell Square.
The Kings cross St Pancras is North of hotel. Maybe we can tube there and then get taxi.
Can you bring the larger suitcases on the tube?

Unless you buy Heathrow Express tickets well ahead, I would suggest taking the Elizabeth line from Heathrow to Tottenham Court Road Station, which would be closer to your hotel than Paddington Station. From there you could catch a cab. Cost would be 12.80 GBP each plus the taxi.

Another, even cheaper alternative, would be to catch the underground at Heathrow, that is the Piccadilly line, continue on that to the Russell Square station which is within a block of your hotel (Which I am assuming is the Holiday Inn.) This would be your most direct route and cost only 5.60 GBP each.

For fares, you can use contactless, either card or phone, you each will need your own.

Edit: for reference a cab from Heathrow has no fixed rate, probably run you up to 100 GBP

I think I see what you are saying about the Express Yellow line. That takes you direct from Heathrow to Paddington, no stops, so a lot faster. I would then transfer to purple line Elizabeth for a few stops, then to blue Piccadilly to Russell Square. If not I can just taxi right from Paddington. That would still save a lot of money.

Thanks both Paul and David for the advice. First time to London. Last minute trip.
Blue Piccadilly would be easiest for me, not having to change, even though it will take longer, since we have suitcases. I assume they let suitcases on the underground train. Holiday Inn is where we are headed.

The least expensive, probably most direct way is the Piccadilly Line to Russell Square and walk a block. Of course you can take suitcases on the tube. In fact, since it starts at the Airport, you should be able to board and have space for your luggage without difficulty . About £18 total.

The Heathrow Express will be quite expensive since you missed the advanced fare discount price. Think £75 to Paddington plus a taxi after that.

If you are going to pay that sort of price, you may want to consider a car service,

The thing to remember is that cars are not necessarily quicker in London. The Elizabeth Line is another option as well.

https://www.blackberrycars.com/ is the usual private hire car firm recommended on here.

I've used Addison Lee around town a lot in the past and they are very professional.

https://www.addisonlee.com/services/airport-transfers/heathrow-airport-transfers/

Here's a link to a Google search with local firms near Heathrow. These may be cheaper if you shop around the top rated ones. More like £50 - £60 to Bloomsbury than £85 - £90 you'd probably pay with Blackberry or Addison Lee.

The Piccadilly Line to Russell Square is your best bet. The morning rush hour is pretty much clear by 9:30am or so. Elizabeth Line to Tottenham Court Road may be slightly faster, but a less appealing (longer) walk to your hotel with a 24" bag.

Just to throw in another little point of discussion, I'd tip a taxi driver a tenner on a £90 fare. Maybe more if it ran over £100. What would everyone else do?

The Holiday Inn appears to be close to Russell Square.

If it is the Holiday Inn Bloomsbury, it is only a block from the entrance to the Russell Square tube station. I used the tube to get to Heathrow when I stayed there.

Just be aware that Russell Square Tube station does have some steps…I believe 12+ ?….before you get to the part with lifts or escalators up to the street.
You’ll have to carry your bags UP them to get out of the station.

Kings Cross has lifts and/or escalators all the way up.
I would take the Piccadilly Tube line to Kings Cross, then a short cab ride to your hotel, or walk to it if you can.
Google Maps says 15 minutes.
It’s flat, I’ve walked that route before with a bigger suitcase, and am doing it again to another nearby hotel very soon.

It seems a lot of us here are all going to be in London at the same time!

By the time you pay for the Heathrow Express or even the Elizabeth line with the walking between train lines, I'd suggest a car service.

It's a fixed price. They meet you as you exit customs, walk you to your car, and drop you in front of your hotel. They will have your arrival information and will know if your plane is on time or delayed. You must book this ahead of time.

It will be less expensive than a taxi.

No stairs, no walking between train lines, no worry about getting disoriented.

If you still wanted to take the train, take the Piccadilly line to Russell Square. It's direct, no changes, you get a seat at Heathrow and get up when it's time to get off. It really won't take that much longer an Elizabeth Line to tube or even to taxi combination and will save you some money. About an hour but could be a few minutes less. (Don't let the Heathrow Express 15 minutes fool you. That's between Heathrow and Paddington once it departs. You still have the rest of the journey.)

Three paying for the Heathrow Express now plus either tube or taxi to hotel will cost as much if not more than a car service direct from Heathrow.

Usually,

BTW, use the names of the tube/train lines not the colors. The colors are just on the map to distinguish the different lines but no one uses them in discussions

The Elizabeth Line is £13.30, not the £12.80 quoted above