Stonehenge is an archaelogical site in Southern England.
East towards London
Go back on the A303 but better you arrive to Amesbury roundabout where there is a gas station with restaurants etc
the best way to arrive is taking the A303 that passes all around the site. Ask your driver to drop you off at any of the small pull over areas along the road, the traffic doesnt go that fast and they can stop easily, if not there are roundabouts couple of km before and after.
Accommodation and Sleep
The meadows down the ruins are perfect to camp, just mind the cows and sheeps! on the upper part of the hill there are also some hippie vans who you can ask hspitality in case you don't have a tent. they have also a petition to make free (legally) the entrance.
Other useful info
Free entrance: the entrance fee is 8£ but you can easily sneak inside from the meadows below it. Just go, entering from the main road or passing from the meadows down, on the opposite side of the official entrance, there's a little hill that cover your bad actions..A very low barbed wire can easily be jumped and you are already inside the ruins area. There walk towards the touristic path and mingle with other people. Pay a bit of attention cause there are stewards around but hardly from that side of the circle. Then enjoy Stonehenge and its energies! When Fede did it (October '13) there were construction works that made even easier hide the view of your free entry, though even once finished the simple hill shold be enough to cover you. If not find another spot, but it's easy the area big and the checks fews