I have recently bought a Samsung smart tv and when the tv is on the Internet speed I get from my home hub 3 is less than 1mbs. When the tv is off I get 14mbs which is what BT have confirmed is coming into the line. Clearly the tv is doing something to the hub. It's not electromagnetic interference as it is the same if the hub is put upstairs well away from the TV. It is the same whether the TV is wired to the hub with the LAN cable or connected wirelessly. Any ideas!? Thanks!
My first thought is that the TV is downloading a lot of data when connected. This may saturate your connection leaving very little remaining bandwidth for your PC. This would cause a PC based speed test to give an unrealistically low value.
Can you try checking the stats on your hup for the amouunt dowloaded, and then plugging the TV in and checking again to see if it increases quickly?