Hello i am currently under the vivid 100 Optical Fibre plan and my experience is pretty horrible since all i recieve with ethernet cable is 1/10th of that. but this is not the worst because usually from 20:00pm to 23:30pm ping spikes when playing online games at the point its not even possible to play.
I am truly sorry for the decline in broadband speeds at peak times. This is due to capacity restrictions on this part of the network and plans are currently in place to implement an upgrade.
The fault reference for this is F004145936 which I've noted on your account. At the moment the review date is set for 26-10-2016 and we'll know at that time if the upgrade is due to commence or if it needs to be deferred. We shall keep you notified of any updates on this.
Please read my PM (purple envelope icon, top right of page) which outlines your credit options.