Theres things you can do to make your connection speed quicker and more stable.
Remove the bell ring wires in your telephone cabling in the house. Only leave the blue wires attached. They are not use anymore by BT.
Use the Main junction box in the house without an extension.
Find out what your noise margin is because this effects your connection if its too low, can lead to disconnections.
for a 4.5Mb connection the noise margin should be around 7-8db
i know i'm rambling on here but people just accept their broadband connection for what it is just because the ISP's say that you might not get what you think, however you should at least get what your line is capable of.
i.e. if your line is capable of 4.5Mb then you should expect to get at least 3Mb if you are less then 2km away from the exchange after that then your attenuation can be affected leading to lower speeds.
Oh god i'm doing it again lol sorry, just call me Mr Jargon.