I have been in touch with ntl regarding my downgrade to 512k a few months ago, a few minutes ago my CM rebooted and when it came back on, guess what, I have been bumped up to 10MB. This is the latest reply I got from ntl via repsonsetek:
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Thank you for your reply. As we have recently changed the details of our broadband again (to a more favourable standing), we have put your broadband back onto the higher level of service. This will give you a 10Mb speed with a 75GB download limit, with this new option if you go over the limit we will put you down to the 1Mb speed but will only be for the remainder of the month that you have gone over. We trust that this will resolve your issue.
I actually wanted to go on the 2MB unlimited service so will contact them again and ask for a downgrade.
Finally, my faith is restored.