ADSL is similar to a leased line in the respect that it gives permanent Internet access at a fixed cost without affecting your telephone line. However it differs in some important respects.
A leased line is a symmetric dedicated service (the same upstream & downstream bandwidth) creating a permanent connection between your premises and the internet through Vodafone.
ADSL is a contented service. This means that it is a best effort network and the bandwidth is not guaranteed.
A leased line is provided as part of a managed service with guaranteed data rates on the line and is covered by business services with the added support features.