Zen is the best ISP I've used, however pricey.
I've heard good things about AAISP, but I just can't accept their bandwidth caps.
Zen have given me fantastic support when I've needed it, and have fully supported me with issues Openreach caused. They activated my line when Plusnet wouldn't. Beyond activation I've had no issues with my line.
I'm glad plusnet couldn't activate my line because I love the great features Zen offer, including a native static IPv6 /48 prefix and a /29 subnet without having to fill out a RIPE form, unlike plusnet. I just wish I could delegate authority for PTR records.
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