It's worth asking OpenReach to check to see if you have a REIN problem in your area. When I had poor broadband speed caused by noise on the line this was the problem. Finally identified as a neighbour's faulty tv recorder that was the cause of the problem.
http://www.kitz.co.uk/adsl/rein.htm
http://www.kitz.co.uk/adsl/rein.htm


