Nildram are to start bonding ADSL connections for users, and will take orders from the first week in December.

Bonding is the process of joining two or more ADSL lines together to make one ADSL connection with the sum of the speeds, less a little overheads (approx 4-6%).

So why bond 2x512Kb connections and not get just one 1Mb line? As BT restrict the upload speed on all ADSL connections to 256Kb the the only way to get an increased upload is by bonding, which would give 1Mb/512Kb.
Also if the line conditions will only allow 512Kb then bonding will enable 1Mb connections, or more.

It all sounds so good, except the cost!! A BT line and an ADSL subscription would be needed for each bond, as well as CPE equipment on the customers premises, which they would have to purchase (a Netopia Router with bonding options is ~£600).

Nildram have said they plan to bond a maximum 4 lines, but have spoken of planning to do a connection with 30 lines!!

While is sounds like a good idea, in practice this is aimed at business users who cannot get SDSL or as a cheaper option to leased lines, as the equipment/rental costs would put this in the reach of only the most of affluent home users.

Some details about bonding ADSL can be found here.

EDIT: Details have now been released by Nildram.