dear Graham:
Well, maybe.... I am not really sure what you mean by sacred geometry. I was trying to express a thought and probably did not succeed in being very clear with it. Sorry!
symbolic field level: In a certain sense, symbols have a reality of their own. A symbol is not the thing itself but it is a useful (to humankind) repressentation of the thing. It evokes the thing for us. The letters t-r-e-e make a symbol (word) which we have assigned the meaning of tree (tall, leafy standing person) so when an english speaking person says tree, another english speaking person will get the idea of tree. Neither the symbol nor the idea is actually a 3D tree but both the symbol and the idea serve to facilitate communication for the people.
In the human mental data banks "lines" have been drawn around the earth. Some are called merridians and represent the north/south lines around the planet (by which location is measured.) I was just referring to the fact that in my limited understanding perhaps the ley lines are the energy level equivalent of merridians. It may be a very poor analogy. Ley lines might be more like the energy equivalent of the plate boundaries or fault lines.
Anyway, I would love to know what they are! Also, now that you have mentioned it, I'd love to know more about sacred geometry! So if you do know about sacred geometry, please share! Blessings, batwings