Heathrow to St. Pancras for Eurostar

Assuming an hour to get through the airport and another hour and a bit to get to St. Pancras, you should just about have time to make checkin for the 12.58. Not much contingency there though if there are any delays en route.

Remember, you have to check in for the Eurostar no later than 45 minutes before departure. That's about 12:10 PM.

One hour to one hour 15 minutes on the tube. There are sometimes delays. So that takes us back to just before 11 AM.

How long it will take to collect your bags is anyones guess. Immigration shouldn't take very long with the egates (assuming you are American or Canadian.) But an hour is a good estimate since Terminal 5 is huge and you may have to take the tram from an outer satellite building to the main terminal. That takes us to 10 AM.

You now have a 25 minute leeway from your scheduled arrival time for delays. Not enough for me but you may like to live dangerously.

Since you are already at Heathrow, why not just look into a flight?

I concur with Frank II’s assessment. Way too risky for me. Why not spend one night in London when you arrive and take an early train next day? Much safer.

I wouldn't chance it. Way too many things could hold you up. All you need is one track slowdown or delay, and you are out of luck. Better to take the later train, or go the next day.

Heck, I'd even look at a connecting flight to Brussels. I've done that, and it was cheaper that just to London (gotta love airline math).

Thanks all. We were able to get a cheap flight for $300 RT each from JFK -> LHR so that's why we did not try to fly directly to Brussels. We have traveled a lot in Europe and have spent a lot of time in London so we wanted to see something else that was reasonably close before we get on the cruise. We decided to go to Bruges. It seems easier (or just as easy as booking a separate flight that may be in a different terminal) to get to the Eurostar since we can take the tube right to the train station. Plus we can get the Eurostar ticket that will include the train from Brussels to Bruges on the other side.

We also have never ridden the Eurostar or gone through the Chunnel so thought it would be fun to do. I have been looking at flights as well but they are more expensive than the Eurostar solution (and I am paying for 5 people so it adds up). We love train travel in Europe.

I think the general consensus is to take the 3:04pm train which I think is the safe thing to do. If we have extra time, we'll just get lunch in the train station or find the Harry Potter stuff!

Still looking for recs on getting to Southampton if anyone has them...

National Express runs buses to Southampton from London. Check with rome2rio.com