Also take a look at:
1.
http://www.corridor-alliance.co.uk/ - still a very active and well informed group indeed even though the link I have looks a bit stale; regular meetings (you just missed one on 14th June), and I can put you in touch is need be. Huge respect for A36/A350 Corridor Alliance and White Horse Alliance Members.
2.
http://www.wiltshire.gov.uk/wiltshireassembly/wiltshireassemblytransport.htm - Wiltshire Transport Alliance of the Wiltshire family of partnerships. I tried to email the contact given over the weekend, but it bounced. Main [council] web page contact form also broken over the weekend -
http://www.wellho.net/pix/wiltserr.jpg so I can't provide much more on this one. I was advised (on Friday) that the group is meeting "sometime next week" and again I can put people in touch if need be. Apparently it's "invitation only" though.
Have I really found a near-complete list? Does anyone have anything they can add? A couple of the organisations on my original list are questionable as to whether they should be included - concerns include whether Wiltshire is just on the edge of their main territory rather than being core to them, and whether they're still active. I have - intentionally - includes those in the "don't know" categories, but eliminated past groups that have rolled into others.