Have looked at Plusnet data for last 60 days and no drops in the overall upload figures. So there is not some generic problem between us and the poster.
As I mentioned earlier there is a pattern where when the poster has high latency their upload is low, 177ms latency is very high for a FTTC service.
The samples recorded for latency during the test were
Idle: [227,173,176,175,169,169,170,141,228,149]
While downloading: [876,643,600,557,605,448,725,845]
While uploading: [226,223,271,191,174,229,218,285]
Given how high the idle latency is, suggests something is wrong with the connection/PC. That latency is not changing much when uploading suggests something is uploading that the poster is not aware of.
The more usual results would be something like
Idle: [16,17,16,16,17,17,16,19,18,23]
While downloading: [42,42,51,54,58,55,47,47,46]
While uploading: [32,21,19,20,22,20,21,17]
Taken from this test that is a similar distance from London and using Plusnet, also notice the shape of the graphs which are more consistent.