Sky might not throttle but some people do see signs of natural contention, so you might not always see line speed.
In areas where there is 'natural contention' Sky have ALWAYS upgraded the backhaul to the affected area within a few weeks.
There was some natural contention issues recently (I was affected). Sky made a list of all affected areas and listed fix dates.
When there was contention in 2011. Again sky resolved all of the problem areas
Net result is that you get full wack everything 24/7.
NO PEAK TIME SLOWDOWNS! It's a commitment made by sky
Torrents, p2p, vpn, everything IS NOT slowed down.
Sky have always upto date upgraded capacity wherever there are slowdowns. They have a tonne of money to throw at their network which they purchased from easynet and boy they have upgraded the heck outta that network since they purchased it.
I'm getting 40 mbps 24/7 even at 8pm. I have sky's fibre offering now. That's 4mb/s even on torrents
This is assuming you are not on sky connect.
So I would argue that you should expect consitent speeds 24/7