Attainable rate just shows what your router thinks the line is capable of, if all restrictions are removed. What limits the actual speeds you get is the package you are on, so no new BT Retail users on Max Premium if they are on the up to 8 Mb service. On ADSL 2+ upstream is usually around 900-1000 Kbps.
There's also Annex M, which shifts the goalposts even further on ADSL 2+, taking some of the downstream bandwidth away in order to increase the upload to around 1.5 Mbps - again, BTwholesale sell this, but BT Retail don't buy it.