yeah I was wondering that myself! It's all very well saying 'on good authority' and not dishing who that authority is!

I've not found anything about the stones being used by the racecourse myself - I'm willing to believe it, but that doesn't mean they weren't recycled from a prehistoric use? They're pretty fancy stones with their holes and wiggles (and those shapes can be perfectly natural, I wasn't disputing it) and naturally attractive to people wot like stones I'd have thought.

All righty, with much thanks to riv, I have much better info.

According to the 3rd Stone article, we have two circles formerly located North of Bathampton Camp (the golf course). Then a main avenue running SSE to the remaining standing stones, this avenue could be traced across the current road and possibly into the field beyond. This places the circles on the slope / edge of the slope down to Bathampton, which tallies with Aubrey Burl's grid ref. Which is nice.
The article also mentions stumps of stones / fallen stones along the path of the avenue from the circles to the standing stones.

Somewhat related, I have an oldish OS map of the area with stones marked on it on the golf course. Time for a good walk about up there (again) methinks.