Low speed after Line Fault corrected

[#1]

I had a Line Fault (mains hum) which caused a low downstream rate for nearly 4 days.  BT cured the fault at the distribution box but rate has remained very low (280kbps) after 3 days and hasn't changed.  The router raised the Sync speed quickly from around 500 Kbps to 2300Kbps on BT curing the fault.  Have rebooted the router but this has had no effect.  I am in the sticks & the usual download rate is around 2Mbps.
Router is TP-Link TD-W8960N and stats are :-
Downstream                                            Upstream
SNR Margin    9dB                                  12dB
Attenuation    64.5 dB                            35.6dB
Sync rate        2300Kbps                        447Kbps
Any ideas on how to raise the download rate to its former value without waiting for the learning mode to take several days to assess the line ?
Thanks

[#2]

There are two possibilities
The first that the BT IP profile hasn't increased - you can check that with the BT speedtest Further Diagnostics http://speedtest.btwholesale.com/
The second is that the Plusnet IP profile hasn't picked up the change in BT IP profile - you can check that here - Current Line Speed https://portal.plus.net/my.html?action=data_transfer_speed