Eurostar to Heathrow

Tube from St Pancras to Paddington, then Paddington Express to LHR, about an hour. That's probably best because you avoid street traffic.

I wouldn’t bother with the hassle and expense of changing to the Heathrow Express at Paddington. Just get on the tube at St Pancras and take it all the way to Heathrow - it takes about an hour and costs about £6. There’s really no need to change trains to the Heathrow Express - the actual train time might be slightly faster but you lose the time by changing trains and waiting for the next Express.

HOWEVER the Eurostar can get horribly screwed up by various things - one train gets a technical issue, or someone jumps on the line (I got delayed like this) and the whole service grinds to a halt. I would not travel from France on the day of my flight home from London. I would get to London the day before.

If you are planning to travel from Paris to LHR to catch a plane on the same day, that looks to be an Engraved invitation for disaster.

Strongly suggest you plan you days in London at the end of your trip and not make a run to LHR from Paris

Heathrow Express tickets are reasonably priced, if purchased well in advance

I agree with Jane - take the direct tube from St Pancras, which is easier than the Heathrow Express.

I too have experienced long delays on Eurostar and I wouldn't risk travelling back from France on the same day as an outward bound flight. Stay the night before in London or at Heathrow.

You need to be at the Eurostar terminal ideally at least an hour before your train. Say 2.5 hours for the train journey. Allow say 1.5 hours to get to Heathrow you will need to be there at least 3 hours before your flight. That's 8 hours plus however long it will take you to get to rail station in Paris, with no wiggle room. Then you have a long transatlantic flight. If something goes wrong with one of these transport links, then your return flight is in jeopardy and you risk having to buy another ticket at short notice, which will be expensive. Leave plenty of time.

Heathrow Express tickets are reasonably priced, if purchased well in
advance

That may well be, but you’d still be paying extra for the hassle of changing trains.

We annually travel between London and Paris as you have planned. We always return to London from Paris two nights before our flight home to the US. We lately have stayed at or near LHR the night before our flight regardless of the time of departure, flights which are always early to mid morning. There are a host of hotels around Heathrow and are listed on the Heathrow website. We stayed at Travelodge Heathrow Central two weeks ago that is serviced by the Hoppa bus directly to Terminal 3. Check in is at 1500 so we sometimes tube it to our Heathrow hotel, leave our luggage, and return to London for a pleasant last night dinner. Stress free and relaxing is the way to spend your last night there.

I'm going to agree with others.....Piccailly line direct from St. Pancras/Kings Cross to Heathrow. You won't save any time switching trains at Paddington but you will save lots of money by only taking the Piccadilly line. It will take about an hour.

I also agree that taking the Eurostar from Paris to London the same day you have a flight is risky.

Now trying to sort out our return. How long does it take once off the Eurostar to get to Heathrow?

It is safer to return the day before your transatlantic flight. Spend the night in London. While Eurostar is usually on schedule, I’ve had two significant delays on Eurostar over the years (one was more than 6 hours delayed).

If you are going to try to travel the same day, I’d be more inclined to choose a direct flight from Paris to LHR that arrives well before your transatlantic flight.

Thanks all for the advice. We are now going to come back the night before and stay close to Heathrow as we have a 10 am flight the next morning.

This may sound pedantic and nit-picky but I would come back the DAY before not the night before. You need to allow some time to catch another train if needed so don't take the last train out.

Well, if you'd said 10 am flight from LHR, everyone would have said right off to spend the night in London. Looks like the first train doesn't even get to London until 8 am, and you should be at LHR by 7 am

Hello,
We are flying out of Heathrow to Washington DC at 4 pm on a Wednesday. We don't have the option of staying in London the night before. I'm debating on Eurostar vs flying. Flying seems like a real pain as we would have to check bag twice and have to deal with all the security lines at the airport etc. Plus we will be in central Paris, not too far from the train station. So even though flying is faster, once you factor in having to be their early, checking bags, retrieving bags, going through customs etc, it doesn't seem much faster than the train. It's also more expensive to fly.

Is it really that risky to take Eurostar to Heathrow the same day as a 4pm flight? If we arrived at St Pancras by 8:30 or 9:00, it should work right? I guess we don't have much of a choice. If there is a problem with Eurostar that day, then I guess that's what travel insurance is for?

I
Assume about one hour give or take 15 minutes for the tube from Kings Cross--across the street from St. Pancas--to Heathrow. Then, depending on which terminal, give yourself another 15 minutes to walk from the tube station to the terminal. Two to three hours for check in depending on airline and whether or not you check bags.

As long as the trains run on time, both Eurostar and Piccadilly line, you should be okay. That being said, the Piccadilly line has been known to have signal problems around Heathrow so be prepared for a detour that could eat up time. Not sure if that would be covered by travel insurance.

So, give yourself lots of time. If everything goes as planned, and you arrive early at Heathrow, there are plenty of shops and restaurants to keep you busy.