Windy1
If you look at my post a few back you will see that I too was paying £24.99 a month. I had originally bought 300k for that price and had been steadily upgraded to 750k over the years. For exactly the same price, using coconutty's link, I was upgraded to 2M. I did have to use the phone to achieve this but it cost no extra and no, NTL hadn't informed me either.
Using the ZDNet Speed test gave me more than 2m.