This. I did the same tour with London Walks probably 3 years ago. Of course, their schedule is quite limited (only on Tuesdays, plus a handful of Saturdays a year, typically around the solstice/equinox) as they aren't really a touring company.

While I was in London a number of my co-workers suggested that I'd find Stonehenge completely underwhelming and to not bother. I didn't listen to them and went anyway. I guess I understand what people are saying when they say that, but I certainly enjoyed my visit to Stonehenge.