Best way to spend day from Southampton to London post cruise

Go to Winchester or Salisbury instead of Bath.

I hesitate to ask, but are you sure that you will be off the ship by 8am? They disembark by highest deck (=highest price) first, so you might be delayed if you are further down the ship.

Anyway, Bath is in the wrong direction. I'd prefer Winchester to Salisbury but both are attractive Cathedral towns. Another possibility is to go to Windsor. Or, the route from Stonehenge to Central London takes you close to Hampton Court Palace.

It also depends where in London your airbnb is. Unless it's in the very centre, you will probably want to avoid central London and go on one of the roads which goes around London for part of your journey. If you are in the centre, or will pass through it, be check if you go into the Congestion Zone and if so, pay the fee to enter (you'll need the registration number of your "van".). BTW - I am sure that you have booked a 6 or 7 seat vehicle, but in english English a van has no seats in the back and is typically driven by builders or people delivering parcels.

Thank you--yes the "van" will hold 6 passengers and 6 checked bags and several carry-ons. I know I didn't use the word they used in my booking.

Thank you for your suggestions--I'd been told Winchester on the cruise boards, but I always like to check here as well. Will contact the transportation company and change things up.

We are going to an apartment near Hyde Park, and have given the exact address to the transportation company, but thank you for mentioning the additional fees.

In my experience the ships alway arrive to port about 6am and if you carry your own bags off you can depart earlier. I am not in a particular rush to get off, but they want you up and out so they can prep for the next cruise that afternoon. Either way we will def be on our way by 10am. So we have basically 10am-4pm.

Although I said I preferred Winchester, Salisbury is closer to your route to London. Also, one of the four remaining copies of the original Magna Carta is on display in Salisbury Cathedral, if that’s of interest to you.

I disembarked Southampton and took the train to Salisbury for my visit to Stonehenge before heading to Heathrow area. If Stonehenge is of interest, what about the other standing stones in the area...Amesbury, for instance. Drive past the chalk White Horse.
Salisbury itself is a cute little town centre with its famous cathedral.
If any of the group read Edward Rutherford historical novels, they may be interested in Old Sarum ruin near Stonehenge.

Thank you all for your input. I did check posts on cruise critic as well and came away with names of 5 recommended companies doing this transport/tours. I checked with each. Only one advised that a stop at Bath would mean 5 hours driving time added for to/from Stonehenge and London-certainly not what we had in mind and they suggested alternatives. Price was comparable to the one we had been leaning towards, so we are going with Paragon Taxis. Had it booked with Blackberry Cars--but feel with our email exchanges they are more a transport only company.

Again, thanks for the input! Cheers!!