Also My First...
As with many above they were also my first ISP proper, having previously been on Prestel*. As I was living at Parents' at the time I did most of my browsing late at night to avoid tying up the phone line (and hoped the "ding" from the phone when connecting or disconnecting would go unnoticed).
I moved over to Zetnet for a while as they were cheaper then Freeserve came out and made more financial sense for the relatively limited use as I wasn't at home very often.
*To email a friend in the pre-Internet days I would dial in to work, initiate a PSS connection to JANET (Joint Academic Network) then onto the Northumbrian Universities network to access a MicroVAX in their department. Login to that and send an email!