I had not seen the post above mine, I only noticed them when I read yours asking if I had... my apologies.
Using DSLReports speedtest things don't look too bad (with a Route Policcy ensuring all traffic goes via BT) -
http://www.dslreports.com/speedtest/70040780
The BQM is still ugly though and I don't have another router I can test with, sadly. As someone noted higher up, contacting BT when I am not using a HH and haven't eliminated the Draytek isn't going to be a nourishing experience so it feels like a bit of a catch 22.
Having got my teeth into this it now feels like I need to get to the bottom of things....does anyone have any other suggestions?