This problem only seems to be for people who have joined SKY, or were moved to them, this year.
Streaming services from netflix, bbc iplayer down to youtube have serious buffering problems. This is not a peak time throughput problem as the victims report it as being at all times, some report it is worse at peak time though.
The start date seems to have been 23-04-2014: SKY have been unwilling/unable to fix it and have been unwilling/unable to even comment on it, not really what you would expect from an isp.
...and yes, I too experience this issue.