Not sure why but since moving from BT to Plusnet my banding is different. With BT it was 80/20 prior to migration, now with Plusnet it's 74/17. Is this something Plusnet have done? Whilst not concerned with the downstream because I've never hit 74, it is restricting my upstream which was always around 19998. My IP profile on BT test is reporting 20mbps on the upstream but I can synch no higher than 16998.
On the 80/20 product, actual throughput is more around 76/18 (with ideal conditions), so you are getting pretty good speeds. If you are sync'ing lower than 80,000/20,000 then other factors have come in to play, for example interleaving may of been applied, or other forms of error correction. Noise/crosstalk/interference may of increased. What modem are you using? Some stats would be helpful in this case.