Upload Speed halved (download fine)

Hi, we went away for a week and on our return the upload speed had halved from 11mb to 5.5mb with no reason - nothing has changed at our end. I have raised a call with Plusnet but they are not responding so was wondering if anyone had any ideas why this has happened ? Below are router stats if that helps... Thanks in advance

Data rate: 5.49 Mbps / 48.15 Mbps
Maximum data rate: 5493 / 48807
Noise margin: 6 dB / 3.1 dB
Line attenuation:47.2 dB
Signal attenuation:19 dB / 47.2 dB
VPI / VCI: 0/38
Modulation:G_993_2_ANNEX_B
Latency type: Fast Path

From BT Broadband Checker Site
Featured Products Downstream Line Rate(Mbps) Upstream Line Rate (Mbps) Downstream Handback
Threshold(Mbps) WBC FTTC Availability Date WBC SOGEA Availability Date Left in Jumper
High Low High Low
VDSL Range A (Clean) 54.7 35 11.6 7.7
VDSL Range B (Impacted) 53.7 35 11.5 7.2

Do you know what the figures were previously for data rate and noise margin for both up and down stream? Also, go by the data rate not the max data rate - max data rate is a calculation by the router (and looks wrong anyway).

No sorry, the Router event log shows a disconnection on 28/08 at around 2:47am which is when I think the problem started but I can't find any connection stats prior to this in the logs.