Broadband works by using multiple frequencies (sounds) to transmit the data. If you remember the days of dial up, you heard lots of squeaks and trills when you were connecting; broadband takes those tones much higher. The trouble with this is that the higher notes get quieter quicker, so if you are further from the exchange you will not get 24Mbps. You can find out where your exchange is by entering your number at SamKnows. It looks as though Honor Oak uses Forest Hill while Crofton Park uses Deptford's exchange.

I live quite close to my exchange, so I connect at 18 Mbps, but you are unlikely to get better speeds with ADSL2+ (Upto 24Mbps) over ADSL (Upto 8Mbps) if there is more than 3000m cable between you and the exchange or you currently connect at between 2Mbps and 6Mbps.

This graph     shows you the approximate relationship between cable length and speed. There are many other factors which affect the speed you will achieve, such as quality of cable, number of joins and proximity to power cables, but it is a good starting point.

If you have a Virgin cable connection outside your house, then this uses a different technology altogether. If you get Virgin broadband over you telephone line, then you will get 8 Mbps max like the majority of ISPs.

Although Forest Hill's exchange was upgraded in February, there were only 2 providers offering ADSL2+ services last time I looked. These were Eclipse and O2/Be

A useful site for comparing broadband services is http://www.thinkbroadband.com/