I had Orange ADSL in the Teal Farm area of Washington and had speed problems especially at night. Now have 4mb Cable.
Had it since end June no problems speed test so far very consistent speed always 4mb whatever time of the day.
You can check at
www.virginmedia.com if you particular street is covered.
I think If you download over 750mb between 6-12 in the evening ( on the 4mb )you are
managed down to 2mb for 4 hours but even that was very steady. You can also check this on the website
Ian