[Sephiroth]

TP-Link Homeplugs have a good reputation. But I can't see an electrical reason why they wouldn't work. If you have ring mains installed in your house then at minimum the Powerlines will work on the same ring. Also if you have ring mains (which you do, I'm sure), then the signal will pass between two rings (upstairs/downstairs) so long as neither ring is isolated at the distribution box (switched off).

It would be a configurational thing, I suggest - or not putting the things directly into a wall socket. The fact that electricity flows to each socket on the ring is the guarantee that it'll work at least on that ring.

Anyway - I'm here and you're right there!