Train from London to Paris and teturn

Buy the train tickets in advance at www.eurostar.com

Your only real option for London-Paris train tickets is Eurostar. Flying into London, then taking the train to Paris to make a cruise has some risks, in the event of delays, strikes, other issues. Leave a big buffer between landing and train departure. You need to be at the train station typically 90 minutes before departure, gates close at 30 minutes before.

Eurostar tickets are best booked well in advance, but then that locks you into a time (see the risk mentioned above) Look at the options, you might want to spring for some flexible option, second class is fine.

Getting from Heathrow to St. Pancras station for the Eurostar can be figured out here: https://tfl.gov.uk/plan-a-journey/ But likely would involve the Elizabeth line to a station to switch to the Underground to St. Pancras, or to a station to get a taxi to St. Pancras. Depends on your tolerance for getting around with luggage, steps, and walking.

Are you planning to fly into London then hop on the train to Paris to board a cruise on that same day? That doesn’t seem to offer much time in case anything gets delayed. Especially if you re flying in from Hawaii. Perhaps you may want to add a buffer into your travel plans.

Which airport are you flying into? If heathrow then the Piccadilly line will take you straight to Kings Cross to catch the Eurostar.

That is hugely risky, in timing terms.

You need at least 1 hour from leaving Heathrow to reach St Pancras, then 90 minute check in, then the train journey, to be at your cruise

The reality is that you need to allow a bare minimum of 3 hours 30 minutes from time of landing to train time.

If your flight is late you miss your train, and maybe your cruise.

You should review flying in the same day, or reconfiguring your flight ticket to be Open Jaw/Multi City into Paris and out of London.

It is hard to suggest a London hotel (or train class) without having an idea of budget, at least.

Yes, thank you for reply. I have more than a 24 hour buffer to get to cruise departure. Will book thru Eurostar tickets but wanted to know if it was worth it for upgrade? Will be traveling very light. Is Uber from airport to train station appropriate? Any hotel suggestions? Have hotel in Paris but not London. Boutique style preferred.
Thank you
PS not coming in from Hawaii...but DEN

Denver to London in December, hmmm. I wonder if weather might be an issue.

Eurostar Standard and Eurostar Plus-
Exchange

You can change the date and/or time of your ticket up until one hour before your original departure time with no fee. You can’t change your destination.
Please be aware:
a) if the cost of your new ticket is more than the cost of your original ticket, you will need to pay the difference;
https://www.eurostar.com/us-en/travel-info/travel-planning/eurostar-fares-and-fees

Be sure you are familiar with the exchange rules in case your flight gets delayed.

Here is one option for a non-rail transport from LHR to St Pancras-- https://www.blackberrycars.com/st-pancras-airport/taxi-st-pancras-heathrow-airport/

One other option.....fly from London to Paris. You are already at the airport.

However, since it would be a separate ticket, you have the same problem as the Eurostar if your arriving plane is late.

Do you a strong desire to take the Eurostar? is your hotel in Paris very near Gare du Nord? Unless taking the Eurostar is a bucket list item or your hotel is within walking distance from the station, I would do as Frank II suggests and fly to Paris from Heathrow.
For hotels in London, take a look at the Standard on Argyle Street.

I've been looking into flying into Heathrow and taking the Eurostar to Paris as well. I'm relatively familiar with London. I plan to just hop onto the Piccadilly line at Terminal 5 to St Pancras. Easy Peasy. It will be about an hour. I see no point in taking a train and a taxi or a train and the tube, when I can just sit on one... I didn't want to fly a short flight (not environmentally friendly) but I compared prices and timing. For me the train is the better choice. Plus I enjoy arriving in Paris in-town, rather than involving another transportation choice from airport to city. But, there are many choices, this is just mine.

I think it would help if you could clarify your timings a bit. I haven’t been able to put the whole picture together. Also, how comfortable are you with handling your luggage? Have you purchased your plane tickets already?

Perhaps use dates.
Dec x leave Us
Dec y arrive Heathrow
Dec? Travel to Paris
Dec ? Board cruise

Thank you all for assistance! To answer... yes the train is my choice as my traveling partners have not done it before. I've done it but I was staying in London. Didn't know how to get to train from airport..
I have allowed plenty of time for mishaps. I leave US on 2nd, Arrive London 3rd... cruise doesn't start until 5th.. time to travel to Paris and enjoy a day or so.
I can easily walk and maneuver any stairs and luggage... only small carry on as I am shipping luggage directly to ship! Yes I have my tickets purchased on BA.. non stop from DEN! Thx for hotel recommendations!!!

Your other option, is that if you do have a day in hand, is to stay in London on arrival day (close to St Pancras) then take an early Eurostar the following morning.

From Gare du Nord you will need a taxi or other transport to the Quai du Grenelle (basically the Eiffel Tower) to embark the ship.

The metro stop is Bir-Hakeim, on Line 6.

Great idea, but I have planned a London stay on the return. Thx for Metro info

Since you'll get to experience the train on the return, I would strongly recommend flying from Heathrow to Paris.
Eurostar is likely to be a mess in Fall 2024 due to the planned implementation of fingerprinting at border control...

On separate tickets, I would allow at least 4 hours, and preferably 5, between your flight arrival at Heathrow and the departure to Paris, but it would still be reasonably time-effective vs. Eurostar, and less stressful.