Will I really get 24 megs?
The actual bandwidth that you will receive is based on three factors: the length of the wire that connects your premises with the BT exchange, the quality of the copper, and signal interference from other users or devices. If the quality of the copper is perfect, and there is no line noise, you will receive 24 megs up to a kilometre from the exchange. If your line is two kilometres long then you can expect to receive up to 15 megs. Your bandwidth will decrease further as line length increases, and we do not offer our service if you are further than 5.5 kilometres from the exchange. While bandwidths are not guaranteed, we do offer the highest bandwidth available using ADSL2+ to your premises.
So basically they're not promising 24mbits so they can give you 1mbit and you can't do fuck all.
Also you need a cable or wireless connector that can handle up to 24mbits.
I wouldn't change to them. NTL for teh win.