What package are you on if you don't mind me asking. Only I've seen that the lower packages have upload thresholds that would cut in after an hour and reduce the stream quality significantly (https://my.virginmedia.com/traffic-management/traffic-management-policy-thresholds.html).
Thanks
I was on 200 Gamer at the time (now deprecated), and am now on the 350 package. Both have the same upload.