London to Salisbury and Stonehenge

Either one will work.
Are you doing this as a day trip out of London and back?
Or will be staying in Salisbury overnight?

If you are good with maps and directions, you can do this trip on your own; which is what I would advise you to do.
If you are not good with maps, directions, and buying train tickets online, I would say go with London Walks. They do an excellent tour out and back.

See this recent thread where this trip was discussed:
https://community.ricksteves.com/travel-forum/england/stonehenge-salisbury-day-trip-from-london

We did this trip in May 2016. Took the train out from London. It was not a day trip for us; we were staying in Salisbury for several days. We had no trouble buying a ticket on the Stonehenge Bus, going to Stonehenge, afterwards walking around seeing Salisbury with the map we were given at the TI (Tourist Information) office.

Agree with the previous comment. Bear in mind that Stonehenge has a large & fascinating visitor centre (indoor & outdoor) as well as gift shop and cafeteria. so there is lots to see; it's not just standing around looking at the stones. You can walk from the visitor centre to the henge itself, or ride a free shuttle bus. If you're really keen to walk a lot, you can go all the way to Woodhenge and Durrington Walls -- about 2 miles, and located outside the eastern edge of the Stonehenge property.

See https://www.nationaltrust.org.uk/stonehenge-landscape/trails/circular-route-from-durrington-walls-to-stonehenge

Also, the bus to/from Salisbury allows you to stop at Old Sarum, which is also beautiful and interesting. Facilities at Old Sarum are more limited; just a small gift shop and I believe there may be a public toilet near the car park.

If you decide a tour would better suit your needs, I understand Pat Shelley is excellent though can't vouch personally. http://www.stonehenge-tours.com/index.html

My 19 year old (at the time) daughter and I paid a little more and booked a small group tour which allowed us to visit Stonehenge at sunrise and walk amongst the stones. Most visits keep you about 25 feet outside of the stones and let you walk in a circle around the perimeter. We got to bypass the chains and had about an hour to wander within the circle and had a personal guide to answer questions for us if we had them. It was so very worth the extra money. We booked it as a long day-tour followed by a trip to Lacock where we ate a traditional English breakfast at an old pub dating back to the 1500's, walked around the town (where many scenes from Harry Potter and Pride and Prejudice were filmed. Then we ended in Bath where we had scones with clotted cream (on our own- and they were yummy!) and then toured the Roman baths. I highly recommend the experience!
Lisa

It will be a day trip from London. We would love to do the inner circle tour, but I don't think you can get public transportation that early/late depending on the tour time.

I'm not sure there is much to be gained by the inner circle tour. I did it once years ago. When we went to Stonehenge in May this past spring, we just did the "regular" viewing, where you walk around the outside of the circle of stones. There is a paved pathway that goes most of the way around the outside of the circle. At one point, we were about 15 to 20 feet away from the closest stone. I do not think Stonehenge is made any more interesting by being able to walk into the stones on the "inner circle" tour. You can see the "inner circle" from the regular walkway around the stones. There's nothing to see in there that cannot be seen from the outside of the circle. I think it's just "hype" to get more money out of you. Save yourself the extra dollars, and just do the regular visit. It's plenty satisfying.

As far as having a private guide, all the information is already furnished inside the museum and by the audio guide they give you to take with you out to the stones.

You say this will be a day trip out from London. So you will have a limited amount of time to see stuff before you have to jump back on the train to London.
You will have time after Stonehenge to visit Old Sarum. It's a stop on your Stonehenge Bus trip back into town. After Old Sarum, your Stonehenge Bus will return to Salisbury. You can get off in the center of town and walk around a bit.

You will want to see Salisbury Cathedral. It is magnificent. Be sure and see their copy of the Magna Carta on display.
Straight across the yard in front of the cathedral is the Salisbury Museum in an old medieval building. Definitely worth seeing.
The small "downtown" of Salisbury is very interesting. Lots of old medieval buildings now used as shops or cafes.
You can easily walk to the train station from either Salisbury Cathedral or the downtown area.

If you are running short of time, do not get off the bus to see Old Sarum. Instead, use that time to see Salisbury Cathedral.

You will always remember your trip out to Stonehenge, but the "Wow" sight of this day is likely to be Salisbury Cathedral.

London is great, but the countryside of England is fabulous.

Thanks so much everyone for the thoughtful and VERY helpful responses!

You are welcome. I forgot to mention....Salisbury Cathedral has an excellent lunch room. They serve salads, sandwiches, main dishes such as chicken and two veggies, and a good selection of desserts. The selection is much better than out at Stonehenge. If you can wait until you get back into Salisbury to eat, the Cathedral is a good choice. I think they stay open late into the afternoon, so if all you wanted there was afternoon tea and cake, it's delicious. They also have a very cute gift shop with books and gifts for folks back home. All profits from food and gifts go to the upkeep of the Cathedral.

If you decide to spend the night in Salisbury, I can suggest a couple of great little hotels.

Also worth a visit if you have time is the house of Ted Heath, UK Prime Minister in the early 1970s (Arundells ). Close to the Cathedral.

One of the benefits of a self tour is you can set the pace. Even with a great company like London Walks, you are on their schedule. By arranging things yourself you are on your own schedule. Rebecca ( above) has been helpful to me on travel matters related to the London area so I would valeu her advice and private message her if you want more information.

The other benefit of doing it yourself is, of course, financial. We are a family of 4and we were considering the London walks trip, and again all kudos to them but it gets very very expensive for four people and certainly even more for six!

If you have time in London, consider seeing the show Stomp. Our teens loved it: high energy, inventive, percussion, amazing athleticism.

SuzieeQQ