Another test result.
At 5am today I checked and no shaping was active in my profile and I started a youtube video. It ran at full 440kB/s on my uncapped account.
Now the only difference between 5am today and 5pm yesterday - when it ran at a max of 250kB - was that shaping was active yesterday. I leave it to you to draw a conclusion from that.
There could be many other factors, like activity on the network, your local exchange, etc. I'm not saying that those are the causes, but we should test further. If we go straight to shaping as the issue, we could spend a lot of time looking in the wrong place while you're still having a poor experience. I would much rather troubleshoot with you and make sure we're focussing on the right issues