Well, that may well be the case, however, the free open access to Stonehenge presently occurs four times a year for sunrise on the solstices and equinoxes. That's what the original negotiators for the open access asked for.

Presumably, EH would prefer there to be no free open access at all. At least, with the two equinoxes and the winter solstice, they can get it over and done with in the early morning before the paying public arrives.