"My insurance brokers got after me twice (after I ignored them the first time) to get commercial vehicle insurance, because they know I'm self employed. This is simply driving myself in around my locality in my personal car (i.e. not owned by my "business" or anything), to work on people's computers on-site."
I supposed it depends on where you are. I talked to my insurer and they told me that as long as I wasn't in the business of transporting people or goods, I was covered. Using the car as a self-employed person to get from client to client was ok. They do base rates on miles driven each year as part of the cost calculation.