I can confirm what I posted to be 100% accurate, as I haven't long undertaken Sky BB myself.
After the DLM period is over (roughly 14 days from activation), you can call them up and ask them to manually adjust the line. (Request the "Gaming" profile, if you want low pings)
For example. I started at 4096/800 when I started, then I was set to 6240kbps after DLM finished, but had a 10dB margin.. called them up and asked if they'd re-profile my line. Now set to 7500kbps and have turned off DLM.
FYI: Sky's default SNR is 7.0dB.