Stonehenge

The question as to what extent am I convinced by proposed solutions in the following categories is a difficult one as more evidence is continually being found but based on what I know and have learnt so far I'll give it a go.
When?
I think this may be the easier of the points as radio carbon dating can assist with all things carbon based, those finds that are not carbon based will hopefully be in places that can be associated with carbon based material and therefore an assumption can be made taking into account their attribution to the scene along with (hopefully) provenance in place.

By whom?
The eminence of the course providers along with the specialist knowledge and skills of the contributors including Mike Parker Pearson and Francis Prior to name but two.

How?
The rigorous scientific method used.

Why?
A combination of all the above points put together.