"Interesting. NSW has it a bit different. The UVP can be for a number of defined trips within 28 days under the same permit. A>B then B>C."
I think that's true to some extent with SA but strictly the days of travel and route, rather than 'within 28 days' and the BIL should have added the trip from home to inspection station but he wasn't advised of that at the time. In that sense I'm not sure whether he could have stipulated- driving home from Sydney car pickup on say Thursday and Friday and diving from home to inspection on Monday on the same permit.
All he would say from his experience is don't take any counter jockey's word for anything and do your homework.