@TCP speed is dependant on bandwidth delay product.
What you call broadband speed test is useless if you don't check also the quality of the service known as "bandwidth delay". This is key to keep the flow of data constant (e.g. to watch movie and play game, Voip...). and VM cunningly advertise "speed" while increasing the "bandwidth delay"...
do a speed and quality test and see for yourself and see how ISP are cunningly making money by delaying a 10Mbs service into just 300ms (transfer speed (kbps) and Delay (ms): go to http://myspeed.visualware.com/servers/lhr.html