You must be on the edge of exchange area, now days if you can only get 512kbit you are quite far from the exchange, eg. anyone who was in the original 512kbit area in 1997 will be able to pick up 8mbit quite easily now on that distance.
Of course the false game can be played either way, I could claim NTL advertise fantastic packages (digital packages) but they not available to me so it must be false technology.
Also you forgot to mention not all NTL cabled areas can have broadband, does that also mean false technology?