Yes, that's a legitimate speed that I get on a regular basis at the moment. Here's an image of my speedtest.net account including a fair few results...
http://i43.tinypic.com/k3sjg7.jpg

My situation: I'm a student, sharing a house with 3 other people. We've been in this contract since just before September, and from the start we've had some issues. The girl whose name it is in, doesn't spend a lot of time in the house due to health issues, but Sky seem to be okay with speaking to other people, such as my other housemate whose name is on the joint account, so that's not a problem.

I believe they've ran through the typical diagnostics with my housemates two or three times, each time it gets better for a short while and then goes back to yo-yo speed. They've said it looks like a "problem with the line"... But I'm going to ring them myself soon when I have time, enough relying on girls!!! :D

With regards to what could be slowing it down client-side, we only stream music/some movies (low quality - not 'those' kind either... much...), and I personally do a small amount of gaming, which all end up being ruined by terrible lag spikes and such.

I'm just wondering, considering the severely terrible speeds we're getting, what our rights are in terms of cancellation with immediate effect? I feel they're not providing anywhere near the service they should be, and they don't seem to want to listen to us when we tell them we've already done the diagnostics - they just want us to do it again, and get off the phone.

What can we doooooooooo?