we needed fixed IPs to push SMTP delivery when users dialled in
I made extensive use of that - SMTP was the only option on RiscOS at the time, as I remember (unless you paid for a dial-up suite) - and (when always-on came around) I used the fixed IP to serve up files to friends occasionally, running straight into an ftp or web server on my RiscPC. My current ISP offers fixed IPs. I have one, and it's costing me a few pennies over and above the normal subscription.
I have no idea if they continued, but Demon was also one of a dwindling band of ISPs to carry a full(ish) newsfeed too. I had great times on the likes of uk.d-i-y.
Made fairly extensive use of my free webspace too, which included the amazing, before-its-time Virtual Tour of the Aber Valley
Typical vanity website, a lot of the stuff on there is somewhat embarrassing nowadays, but then it was the mid 1990s - the Tour itself went on line in January 1997 and I'd had a Demon account for maybe a year by then?
We dropped Demon during a house move in 2009, it wasn't really Demon's fault - it was BT who decided to cut off our telephone on the instruction of our buyer about a fortnight before completion date and wouldn't admit fault.
The ADSL kept working for a while, but itself stopped a few days later, and Demon was no help either - BT had told them to switch off as part of the disconnection.
When ADSL Max had been enabled on that line some years earlier we went up from our paid-for 512kbps to a rock solid 8Mbps, being about a half a mile from the exchange.
Things are different where we are now, our ADSL2 struggles to reach 5Mbps most days.
Oh yeah, and I did like the fact that the phone numbers mostly ended in "666" :-)