UncleRob,
Great write-up, with interesting theories. Sounds like you had a good day. Like you say, some places are best visited in winter, when the Triffids are a little less well grown.
A little late, I know, but for a future visit, I've just noticed in the back of Loveday's book "Inscribed Across the Landscape, the Cursus Enigma", that he gives the best places to see the Dorset Cursus, as grid references, so here they are:-
ST 969 124 Southern terminal on Thickthorne Down, the only preserved one in the country, with it and the adjacent long barrows on Public Access Land.
ST 994 138 Gussage Hill long barrow, seen from the Jubilee Trail path, but the cursus and all other earthworks are flattened by ploughing.
SU 008 149 Wyke Down henges accessible on Countryside Stewardship Trail, with the seasonal lake.
SU 017 160 Eastern bank of the cursus, preserved as a field boundary beside the B3081.
SU 041 191 Bank barrow beside northern terminal of the Pentridge arm of the cursus, seen from the footpath by Bokerley Ditch.
SU 024 103 Knowlton henges and barrows. The Church Henge is protected by English Heritage.
You probably know all this by now, and I wish I could have informed you earlier, but maybe it'll be useful for others.
Cheers,
TE>