ADSL available everywhere?
ADSL is available in nearly all of BT Exchanges. However, the distance from the exchange must be less than a certain figure and quality of wiring and connections can affect connectivity and speed.
Why is the download speed greater than the upload speed?
ADSL is Asymmetric which means it runs at different speeds for upload and download. There is also a service called SDSL (Symmetric Digital Subscriber Line) which runs at the same speed for both upload and download