After cleaning out the garage, and accidentally powering off the surge protector the PSU is plugged into, I have no internet. The BBU beeped for a second and then the whole system powered off,
I switched the surge protector back on - PSU light is green / BBU has no lights / ONT has no lights.
Try removing the battery from the BBU and unplugging the PSU. Then, plug the PSU back in with the battery still disconnected. If that doesn't work, then let the technician handle it.
Oh, from now on plug your PSU directly into the wall. Switched outlets are bad when it comes to FiOS power supplies. If you're that concerned about surges, get a whole home surge protector as surge protector strips don't really protect.