Hi, when I first tried to get Broadband, I discovered I had a BT shared line (DACS). I tried a few ISP's but all backed off when they discovered the DACS line. They just could not be bothered with the extra hassle.
To cut a long story short, Zen were the only ISP that were willing to get BT to remove the shared line and enable my connection. All done within 5 days.
Zen are not the cheapest but they do go that bit extra to help out their customers. Have been with them a few years now without any problems.
Newnet maybe another to look at.