So it may seem like a bit of a pain, but what you really need to do is reduce the setup to as close to default as possible. In this case, that would be connecting your computer directly to the Hub without the TP-Link or any PowerLine adapter connected. If you get a decent speed, then it's going to mean that whatever is causing the issue is somewhere in the intermediate devices you are connecting. Personally *in most situations* I would let the SmartHub do it's SmartHub stuff, and have the TP-Link device set up as an access point!
I only learn by making mistakes and owning up to them - boy do I learn a lot!
