AO,
Personally, knowing BT's abysmal level of customer service, I would pick a decent LLU ADSL line over any BT broadband product, fibre or otherwise.
Once the 21CN wholesale rates start dropping, you'll see LLU-style offerings over fibre. But will probably take some regulatory intervention to force BT to share some of that fibre infrastructure with others at a fair rate (well, fair as far as BT's pricing structure goes anyway !).