I'm on Octotel and have zero issues with CISP. Stay in the Claremont area
I too stay in Claremont with Octotel. 100/25 line.
The reason I say its congestion is because my issues only occur during peak time. I can give you a day breakdown of how the internet functions.
Mon-thursday is a mixed bag, at best twitch is unstable but usable at worst its unusable.
This is typically what I get in the evening (between 6-10PM) on these days:
London (Coreix) Single-Threaded:
Friday is the best day of the week. Most of time its usable but can be unstable.
Saturday is also a mixed bag.
Sunday is without a doubt the worst day of the week. My international basically grinds to a halt and its outright pointless trying to stream twitch or anything international.
Sunday throughput:
London (Coreix) Single-Threaded:
I'm using single thread performance here for the sake of brevity and because its accurate to what I get throughput wise to twitch in evenings.
Over the Christmas break, I had flawless internet for about 3 weeks. Any time of day or night I could stream twitch without any issues. Once Jan started the internet went back to what you see above, basically unusable.
My issues started back in October and I've tried everything on my side to fix this, even bought a new router which obviously has done nothing.