I too have been with Zen for years. Fortunately a /32 is all I've actually used but it used to be the case that if you called them you got through to someone who knew their @rse from their elbow straight away, and that's very much not the case today.

They recently made a complete mess of my 82 year old mum's fibre / VOIP migration (didn't even tell her about any changes until her phone stopped working and then shrugged their shoulders when I told her they'd left a vulnerable person living alone outside cell coverage without
any means of communication).
It was a challenging enough time for her living alone for the first time in her life, with my dad having had to go into a care home.
Multiple calls pointing this out to Zen got no traction whatsoever and eventually a letter pointing out that both of us had been with them for 20+ years and would be pulling the plug if this didn't get a timely response got them off their @rse but not until her comms had been completely cut off for 2 weeks.
Fortunately, she was back online by the time the call we'd been dreading arrived but I shudder to think what might have happened if she'd had a fall while they were dicking about.
They still haven't sorted out the FTTP upgrade 3 months later. They've just been sending muppets from Kelly communications around, which will never achieve anything. "Oh, that's the wrong type of telephone pole. I'm not allowed to touch that".
