Well I guess I agree Stonehenge could well be 'about' grain, because as you say the landscape around that time was being cleared, and plants were being domesticated. And you'd need to sow and reap your plants just at the right time - an astronomical 'instrument' would come in handy.

But isn't the carousel thing rather over-egging the pudding? I mean, Occams Razor and all that. Are there any post holes in the right place as supporting evidence for your theory? The central post for instance. That'd make a bloody big hole. I know you said they could move it around, but it would have to be huge and if it wasn't secured at the top it'd have to be secured at the bottom or surely people would get squashed?

I love my folklore and I notice you say "Old stories of sound coming from Stonehenge may be folk memories of the grinding and rumbling noises of the working mill." I haven't spotted these before and am intrigued to hear more / where you got this from.