Just to confirm, are you connected to your router via ethernet cable? First thing might be best to try is change your DNS settings to see if that helps, then do a speed test after. Take a look at the link above if you need more info about DNS settings.

Yeah Ethernet but through power line adaptor, could the adaptor be the problem? I'll try that.

If it doesn't have an external way of showing you the line quality to the other home plug, then try different plugs. Avoid using it in multi adapters if you can. I use one in my house as the hub is two floors down. Too much wi-fi interference so used home plugs. But the line quality was really poor up in the top of the house, so had to run the ethernet cable down the top flight of stairs to middle floor and now getting fastest speed I can possibly get. When I had speed of 6 to 7mbps I was getting disconnects on a lot of my games, but it might have been a combination of that and a, then, poor connection quality. I'm now getting upto 13mbps download and 1.1mbps upload, also on bt using homehub 4, but don't have any disconnects.