Thank you to the Mods and those who posted to help. I'm happy to report that the correction to how my service was provisioned has been applied, and after a short interlude whilst Openreach fixed a broken wire between my home and the cab (how's that for bad luck), my service is now performing as expected.
DLM is still doing it's stuff but you can see from my stats that having moved away from the problem I was having with my Sky service, I am now heading back towards the kind of speeds I was expecting and hopefully DLM will drop my Noise Margin to 3db and squeeze a little more out.
DSL uptime: 0 days,07 Hours29 Mins00 Secs
Data rate: 10.558 Mbps / 62.062 Mbps
Maximum data rate: 10.681 Mbps / 63.658 Mbps
Full Fibre (FTTP) Mode: Off
Noise margin: 6.5 / 5.1
Thanks again for the help received