My connection has been at 1Mbps for quite some time.
According to my local exchange information, it's been upgraded recently for MaxDSL. I've also received an email from PlusNet to say they've upgraded me to the new (up to 8 Mbps) speeds but due to exchange problems were unable to put it at any more than the current 1Mbps.
However, when I try the (admittedly crude) online estimation tools it suggests I should be able to get around 4Mbps.
My stats are 1152Kbps, Line Attenuation 55db, Noise Margin 20.6db