Any LLU invariably runs on ADSL2+ these days. Upstream is usually 1.1 - 1.2 Megs (some BTw based systems only give 888 K on Interleaved, but that's not Sky) unless you have a very fast line and can sacrifice some downstream to get an upstream of about 2.5 Meg with ADSL2+ Annex M. I don't know if Sky offers Annex M.
The fact that your exchange is not 21CN WBC enabled is irrelevant to LLU; it is only available on BTw based ISPs.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC