A pretty good test as an alternative to Java based testing for measuring the downlink is to try downloading the 15Mb test file from the following link:
BT Openworld
When the transfer is around 90% complete, take note of the transfer rate. Then multiply this by 8 and devide the result by 1024 to get your effective speed in Mbps. For example, I typically get 321KB/s on my Digiweb 3Mb DSL link, which gives (321 x 8) / 1024 = ~2.51Mbps.