Ah... Spoke a bit too soon.
Everything was ok, until it went under load, and the router tried to reboot. To be fair the router hasn't had a firmware upgrade since 2005. (CISCO at home HG200 and there isn't anything new
So I have replaced it back with my Netgear DGN2200 ATM. (Still SNR at 9 but sync at 5.5k)
As I haven't got a decent back up router anymore are either too old (D-Link DSL-504), or BT home hubs (Which I remember had a load issue on my wireless).
I have bought a billion 8800NL to replace it with (It also has the added advantage of being 17a fibre compatible when we get it).
One thing I wanted to ask I see the router is capable of tweaking the SNR margin on ADSL. If I played with those settings. Apart from the risk of stuffing up my own line, am I likely to causes issues with contention on the line for somebody else?