As I was getting good error stats on my long wire from the exchange, I asked to get interleaving switched off on my line – i.e. fastpath. So with nothing else apart from standard ADSL2+ and fastpath I get:

And I get the following summary from my Netgear DG834PN

ADSL Link	Downstream	Upstream
Connection Speed	6100 kbps	1157 kbps
Line Attenuation	48.0 db	24.7 db
Noise Margin	6.1 db	6.4 db

Assuming things stay stable (based on the advanced stats) I will go for a lower noise margin profile.