Check for local issues on : 0800 561 0061 - it is an automated service.
If yours is Hub (3/4/5) is in Router mode, test the speed to the Hub vs speed at the device : https://www.samknows.com/realspeed/ once the test starts click on Run full test this will show the upstream figures.
I'm really sorry to hear of the upload speed issues. I have checked the system for you today and you are affected by an SNR issue (signal to noise ratio). F010309610 - this is the fault reference for your records. The estimated fix date is the 3rd February at 9am. I hope it's fixed sooner for you but please monitor the speeds and connection after this time for me and report back any issues.
Thank you for reaching back out to us and for the update, really glad to hear this is now resolved, can you expand a little on what fixed this, any information that may help other is greatly appreciated?