Used those Powerline adapters in a couple of houses I rented and they work well. But for some reason, in my own house with up-to-date building regs, they don't work...at all.
If you think about it, old houses had one single circuit that some electrician hodge podged together and daisy chained off the room next door. Effectively it was one long cable doing your entire house nearly.
New regs came in which mean that each room now runs on a single loop straight back into the board. Even large rooms are sometimes broken into separate loops.
So in an older house the signal comes in and flies straight up to most rooms in the house but in the new house it goes in, does a loop, goes to the board, does a loop and on and on until eventually it comes to you with piss poor signal.
Or so a technician told me he came out to install my broadband.