Bulldog is fast, very fast. But customer support is awful. They used to be a small company with 20 on their suppport team. Now with a huge promotion, their users and profits are up, but support has hardly been touched.
Alot of angry users found they were without a phone or the internet for weeks on end. I suggest you dont go with them. There are alot of complicats about Bulldog involving connection issues. Also your current isp is not that great. I suggest BT, or like me Telewest. But I use Telewest because I have their cable services as well.
I hear NTL is boosting their connection speed soon, but Telewest support is great. My connection has never gone down, and my cable box has been upgraded for free 3 times now. They really look after their customers.