I moved to a flat with Openreach fibre already installed and assumed it would be quick to set up a connection there. However, I'd ordered multigigabit service and apparently Openreach wouldn't run anything at all prior to an ONT upgrade. The first upgrade appointment was missed and on the second one my service worked for about 15 minutes then failed, which their support people put down to the order not having been marked as completed. Eventually, another engineer visit was arranged (apparently, there was an "exception" of some kind on the Openreach side), and my connection has been running fine since.

Most of this inconvenience was of course an Openreach issue, but Zen were not good at persistently tracking the status of my order for me and keeping me informed, though they were reasonably helpful when I called myself.