Right Nigel, raising the uprights.
I have only ever had one go at this but from what I learnt I think it is possible to drop one on a sixpence time after time. Note the word think.
The method works like this, Dig an hole with the same profile as the originals at Stonehenge. working from inside the circle move the stone base first so that it lies with the base just about one foot past the far side of the hole. Raise the stone to an height of about 12 ft supporting on two seperate towers. position the collapsable "A" Frame on the far side of the hole and lever up the stone a few inches so that the stone now rests on one tower and the "A" frame. Remove the redundent tower and then collapse the "A" frame. Providing the stone is positioned right at the start it should drop on the same spot every time. It should be possible to ensure that the tenons are the right disance apart when the stones are vertical. (The BBC put the second upright in with a crane by the way) I do not propose we cheat an any way whatsoever.