Hi @TCooke and thanks for posting.
I'm sorry this has happened. As @Webby has mentioned this has happened before and unfortunately there's not much we can do about it. We can take a look at this and see what the best option might be for you if you wish. Can you drop me over an email with your details? You'll get the contact the moderators link in my profile.
This is disgraceful. I'm shocked that BT or any ISP for that matter can get away with disconnecting someone from a FTTC connection to be put onto an ADSL connection without notice, disgusting.