Two of us are travelling from the US to London, Heathrow arriving around noon on 8/19. We need to be back in South Hampton by 8/23. During that time, I wanted to go to Paris, but also spend some time in London. Would it be best to take the train the day we get there (after being on airplane direct flight, but on USA time) to Paris for 3 days, then come back to London, then train to South Hampton later in the day on 8/23 or does someone have some better ideas? We will have luggage in tow. Any suggestions are welcome...just don't know the logistics of this travel idea....
Personally for convenience I would want to avoid doing the same journey twice - so would fly to Paris (direct or otherwise), do Paris to London by train, and London to Southampton by train. However, what you say suggests that you already have arrangements to Heathrow. In that case I would do London first, train to Paris, and fly from Paris (Orly) to Southampton Airport, which is about 4 miles from the centre of Southampton. Booking now for August has probably missed the boat for the lowest fare on some of those however. (Always Southampton not South Hampton - important for travel searches.)
What time do you have to be in Southampton on the 28th? There are 3 Flybe services from Paris Orly to Southampton, two are already full and flight BE3042 arriving at 10.30 has only two seats left (at the time of writing, and at €56.60 each with 10 Kg of luggage, €92 with 20 Kg). EDIT - I need reading glasses. So, it's the 23rd. Not looking great - there are seats with a 20 Kg luggage allowance on the flights arriving at 17.45 and 21.30, but even the later one is €120 each. If that isn't attractive, then train services to Southampton leave from London Waterloo. There are generally 3 per hour and it takes around 1 hour 20 minutes. If you get the Eurostar back from Paris then you come in to St. Pancras International, so on the Tube that would be Piccadilly line to Leicester Square and then the Northern line down to Waterloo, amongst other routes. With luggage I might consider getting a cab instead.
Oh yes. Southampton Airport has its own railway station, just a few yards walk from the terminal building. Frequent trains will get you to Southampton Central in about 10 minutes, then assuming you need to get to one of the dock gates to join a cruise, there are taxis just outside the station (use the exit barriers on the platform your train comes in on and you will see the taxi stand to your left). All of the dock gates are no more than 10 minutes from there by car.
23 August is the Friday before the August Bank Holiday weekend which probably doesn't help - although capacity on PAR->SOU is not great at any time.