I have 50mb fibre and its constantly buffering every few seconds it stops, when trying to watch 1080p video. Surely this should not be happening with fibre.
Also when I had it installed the wiring work was shoddy to say the least. when an engineer was out to fix a fault, he noticed it and said he would get someone sent round to sort the wiring out. Months have passed nothing has happened, now the wiring is off the wall and a trip hazard.
If wireless, try wired directly to the hub with a Cat 5e cable or better with a device equiped with a gigabit ethernet network card, as we need to determine if it is the actual internet connection dropping or just the wireless signal between your device and the hub.