A little difficult to follow you're story because it's pretty much one very long sentence.
Let me try to summerise:
You were originally on Wanadoo Anytime, but they asked you to upgrade to BB.
During the upgrade you ask if there would be any charges if you moved house and they said no.
When you actually moved they charged you £25 for a service you have not received.
Am I correct there?
If so, are you still being charged a monthly subscription?
My advice would be to get your story into order, chronological bullet points would be good, along with copies of bank and/or credit card statements, then pop along to trading standards to see if you have grounds for county court action. As I see it Wanadoo have reneged on an agreement not to charge for moving your service, and they are charging you for a service you have not received.