Isn't that the one with Julian Richards? It's been a while but from memory it's a good experiment and uses reliable information, not whishy washy stuff.
National Geographics docu about the Stonehenge Riverside Project first broadcast this time last year and narrated by Donald Sutherland is a fairly well put together docu about the project itself and stuck to the facts that were being uncovered. There was the odd little thing that seemed to be put in for dramatic licence that slightly bewildered my colleagues and myself (I've just fininshed working for NT at Stonehenge), but it seemed ok overall.
This year there should be a new NOVA documentary about last years Riverside Project, and a Time Team Special as well.
There's another documentary that I can't remember the name of featuring Mike Pitts as he creates Foamhenge, and although it seems a rather gimicky concept it's actually really good.
Don't watch the Timewatch Bluestones documentary, unless you want to get really really angry.