Don't think much of Office (21CN)! It just offered me 8 Meg speed on a line that's currently getting 20 Meg on WBC (that;s the real title of BB on 21CN exchanges)
Other than the IP Profile, which is more direct on WBC, 21CN and LLU are much the same as they both use the same ADSL2+ technology over the same copper. the only diff will be how the ISP manages the line.
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