I'm not sure this is co-incidence or not but I just upgraded the firmware to 2.32c and my downstream line rate is now stuck on 4000 kbps no matter what I do with the SNR setting (I used to get ~5800kbps). The upstream rate varies a little. The coincidence part is that I've also just requested a MAC code from my ISP to switch to Sky fibre.

Cheers,
Kenny