By way of an update, my Aquiss FTTP 300/50 FTTP service was installed three weeks ago and (tempting fate here) it hasn't missed a heartbeat.
My ONT is connected to a Fritz!Box 4060AX router and a Fritz!Repeater 3000, and I am getting near 300/50 speeds around my home. The 4060AX also has an inbuilt DECT base station which is connected to AAISP's VOIP phone service.