Righto something I have forgotten to mention.
Theres quite a few speed camera's on the A303, one by Solistice Park Services, then another one in one of the villages a bit further on, then another where the you come through a 50 limit and then go up a hill. Then another set on both sides of the road on one of the single track carrigeways.
Theres also another on the 50mph single carrigeway section between Sparkford and Yeovil. Just before the turn off for Yeovilton.
They are all static cameras and painted bright yellow so if you get flashed you're a muppet...
Also the scamera van likes to lurk around the Meare turnoff on the over bridge above the A303. Also on the section near Sparkford the police used to like pulling people for speeding on that bit to.
Its mainly the single sections of the A303 you want to keep your eyes peeled on.