Slow YouTube speeds

[#1]

I've got a line showing good ADSL speeds (4meg down). But I'm experiencing very slow youtube speeds for a couple of days.
Other sites seem to be fine.
Is anyone else getting this? How can I diagnose this problem?

[#2]

Hi retrocool,
We are having issue to do with traffic management here at the moment, as posted in our service status here
also affecting certain sites as I've explained here
Jojo

[#3]

Locked in favour of master thread.