Don't tell anyone, but my sync speed has gone from 8Mbps to 14Mbps for no apparent reason!
I'd be surprised if you were automatically moved from an ADSL1 to ADSL2+ product, due to the changes in the pricing.
When you go from 20 to 21CN, your product will stay on ADSL1 tech, due to the above pricing difference, and, as someone else has said, ADSL2+ doesn't necessarily work will with all connections. Its all a bit weird to be honest...
Well, I hope you enjoy your new speeds!