It would help but it won't get anywhere near 1Gbps. Powerline kits just aren't that good.
Have you thought about running an ethernet cable from the Hyperoptic port to a better position for the router? This doesn't have to be an ugly cable that goes around door frames - the layout of my flat allowed a freelancer to go through the utility cupboard wall and underneath the kitchen units to reach the living area.
Unfortunately that's not an options as its a rented place.
On 5ghz I'm hitting around 400mbs right next to the router. This is dropping to around 150/200mbs in areas that I use it most (approx 5 meters away from the router, although through walls). I know I won't get 1gbps over WiFi but I was hoping the Powerline might take it up to the same as it is by the router?
This sounds fast, but I was hitting around 300mbs with BT previously. Also, it doesn't actually seem as fast as it is stating - e.g. videos are buffering for ages, pictures aren't loading on websites which wasn't happening previously with BT.
TV, PS4, Xbox One and PC are all plugged in to ethernet and are hitting around 700-900mbs. Seem to be running fine but again, slower than they were with BT even though the speeds are 500+ faster on the tests.
My flat has an inbuilt network cabinet with an 24 port ethernet switch that links to ports around the flat. Could this be used in some way to boost the WiFi?
The router is Tilgin 2381