Of course your speed is going to vary with ADSL but before the upgrade what speed were you getting?
This is a quote from the 21CN FAQs page at http://www.btplc.com/21CN/WhatisBTsa...dA/general.htm
"Will everybody in the UK get a 24Mbit/s broadband service?
BT Wholesale has introduced its next generation broadband service – called Wholesale Broadband Connect – into the market place and its functionality and availability will increase overtime. Where end users' are connected to a 21CN broadband-enabled exchange, communication providers can choose to supply end users with products based on these next generation broadband services.
The ADSL2+ equipment deployed in exchanges supports a theoretical maximum speed of 24Mbit/s and end customer lines will deliver the highest possible stable speeds they can support. However, distance from the exchange, internal wiring, interference from electrical appliances and other factors will continue to affect an end user’s broadband speed.
But there is more to next generation broadband that speed. It opens the door to greater control, choice, flexibility and differentiation. WBC can prioritise different types of data running along the end user’s line and its specially designed software changes the dynamics of each line so the service is more reliable and runs at optimum levels."
I am not sure what speeds you are expecting but the 21CN is not just solely about upgrading speed. Its about upgrading the outdated and crippled network for the next generation.