Broadband Max Download Speed

[#1]

Currently with BT, but moving to Plusnet shortly (8th May).
Sync speeds are current 8128/448 (200m from the exchange  ), but my router, a BT2700HGV, reports a max speed of ~10000 (can't remember exactly) downstream and 1024 upstream.
Any ideas why this is? Only started happening in the last few weeks

[#2]

That will be the router guessing based on the remaining SNR up and down which may have increased recently.
It is only a theoretical value and can't actually be achieved on ADSL1 Max. It may be possible (and more) when ADSL2+ is introduced later this year if your router supports ADSL2+..