the Bustard in is on the road to Larkhill from Shrewton, leave Shrewton on the B3086 (it's called the packway) towards Larkhill, a mile or so along you'll see whopping great corn silos on your left, then a camp and a cross roads, turn left and keep going till you come to the pub, just before the range hut, there's a sign post at the cross roads for it. there's a little community living down that road. took these from google earth if it helps:
the cross roads 51°12'2.48"N 1°51'46.01"W
the Bustard inn 51°12'49.12"N 1°52'12.68"W
We used to take lots of pics while out and about on the plain, and at Imber, any thing your not supposed to photo is generally marked.
hope this helps.