It seems that the budget ISP/reseller world is a very unhappy place at the moment, as V21 customers will tell you.

The ISP was bought by Biscit last month, but yesterday customers found that they had been cut off and found themselves faced with a page, hosted by rival ISP ezeeDSL (a subsidiary of 186k), explaining that their ISP no longer had any web services.

V21/Biscit's customers could ensure "service continuity" if they entered their credit card details and signed up for a new 12-month contract with ezeeDSL/186k and  any customers who had already paid up front for their V21 contract would have to take the matter up with V21 directly.
Any customers who were unwilling to do this would have their service cut and would have to wait 10 days for BT to "action such cease requests". Wholesale provider  Netservices, who provided V21 with internet access, say that their wholesale distribution agreement with V21 forbade them from issuing a MAC code which would enable users to migrate to another ISP.

V21/Biscit are understandably a bit upset about this and have decided to sue Netservices for an undisclosed seven-figure sum, but this still leaves many customers left in the lurch.

The ezeeDSL FAQ website can be found here.