"What have the Celts got to do with Avebury? They lived in Austria and expanded south and east in the Iron Age."
Quite.

Littlestone put to much of a mix into one period. The things she discribes are mostly from after 1350 bc after the decline period-Thracian-Greek- scripture- moving into the Iron-Age etc. as the before period is greatly unknown after being rather demolished -this period is Cyclade-Greek, Northen European.
The Greek myths near all come from the new generation of Gods, versus the 'old' ones that not much is known about.

Yes domestication of farming animals has been going on a long time, proberly reindeer, dogs, chicken, cats, sheep, goats, cows, pigs and what have you, I know that Neolithics had a thing about animals, I know that Neolithics knew their stone material like no other. And I have learnt that patterns in the stone are expressed on the stone. Inside becomes outside, outside becomes inside.
Yes these people where very clever indeed.

Littlestone is also ROFLing! But wait 'till you hear my other idea - the one where the Avebury ditch was full of water and used as a Neolithic leisure centre (with plenty of bacon sandwiches to go around :-)