Don't think it will be possible, the migration order will have been submitted to wholesale and you might even be moved by tomorrow morning (Monday).
Your only recourse would be the distance selling regulation to my knowledge, even then your current service provider will become a new provider again as you had left them.
When did you sign up to your new ISP? If it is more than 7 days since you agreed your contact with them then your stuck with the new ISP. Also if your new ISP doesn't let you have a cooling off period you wont be covered by distance selling.
Who is your new ISP, BT?
Edited by deleted (Sun 25-May-08 16:00:10)