I have 2Mb Tiscali,my speeds vary between less than 512Kbs(extremely busy net)and 2.2Mbs(very early hours)
I have tried tweaking connection settings,and only differences are dictated by the net usage,and connectivity for online games.
Previous attempts to alter speeds on a lousy Pipex connection,rarely did anything positive,often making it slower so I returned the settings to "defaults"As Pipex repeatedly failed to address the issue,I changed ISP.
I use PC Pitstops "Optimizer" to tweak my present connection(dependant on my requirements)
Your connection isn't bad,all kinds of things can affect it,including how many others are accessing the speedtest site at the same time.If you still feel cheated,then try contacting Wanadoo for advice/suggestions.