I went with onestream after I moved house.
Waited about a month for installation, and they sent a router which I set up but it wouldn't connect. Used their live chat (not sure this is still available on their site these days) and had an openreach engineer 2 days later... line wasn't connected in the street cab, which puzzled him a bit that they'd try to establish a service without that being checked.
I've spoken to their customer service quite a few times. Always from the UK. And for the most part they all understand what I need.
However...
One of the things they do is bundle in KasperskyAV and a product called OneStream Assured which is on top of the headline price and you need to manually cancel those options, you can't opt out of them at time of signup. Kaspersky was removed on first asking, but onestream assured remained on my bill for about 3 months and I had to ask them to remove it around 3 or 4 times via live chat and phone. Also needed to change my contact email.
The issue seems to be that their backend systems all seem to be separate so the customer service seem to think they've made changes but those changes don't propagate onto other parts of the system. The last customer service interaction was by phone though and the guy seemed to know exactly what was going on and sorted everything, and also rebated the money taken for the bolt on products (I didn't even need to ask for that).
Honestly apart from some of the customer service interactions being a bit ineffective I've found the staff themselves to be quite helpful, or at least they're trying.
Speed & service wise it has been pretty much rock solid, I'm getting the maximum that the BT wholesale checker has given.
I've not had any outage faults so I can't comment on that.
Their account page on their website is also quite sparse - it's basically just a page where you can download your bills as PDF.
I guess everyone's mileage may vary, but I'd say I've had good luck so far. I was with VM (since ntl) at the old house for about 20+ years and they had their ups and downs also, I reckon every ISP will have their bad moments.
