Youtube video playback speeds?

[#1]

YouTube (or any video streaming site) is incredibly slow with a wifi or wired connection on my fibre optic connection.
2-3 minute videos take forever to load and playback is terrible, constantly stopping and very choppy. Otherwise my speeds are absolutely fine for everything else but it's video sites which have problems.
My parents live nearby and are with Sky and the same videos playback in no time at all with their cheap and cheerful connection.
Any ideas what may be causing this? Watching videos online is starting to be next to impossible.

[#2]

Hi there and sorry to hear about the issue you're having. The fibre connection does indeed seem to be performing well and looks to be stable from our point of view.
Running a packet capture using <a href="http://www.wireshark.org//">wireshark</a> could help us identify the issue.
Can you give that a try for us?

[#3]

Just to add, have you tried streaming a video on another device aside to the one you're having issues on?