As I say I dont always trust the speedtest.net test - not on my own line anyhow.
A few tests Ive performed in this order.
Test file from fuller zen.
10.MB in 4sec
rate 2.5MB/Sec (= 20Mbps)
Speedtest.net
Thinkbroadband.com
Speed Down 18468.89 Kbps ( 18 Mbps )
Speed Up 2257.43 Kbps ( 2.2 Mbps )
So since I can download in real-time inc overheads at around 20Mbps.. I go off that and the TBB speedtester.