Power line booster

Best not to buy old / used VM Powerline adaptors from eBay,
the issues are ...

1) they may in fact still belong to VM
2) these are old AV200 spec units have poor speed of operation
3) they are all old / end of life and are now failing with thermal / burnout events damaging sockets and walls.

Much safer to buy new AV1000 units with assurance that the product is actually working & not dangerous
https://www.screwfix.com/p/tp-link-tl-wpa7517-kit-dual-band-av1000-powerline-adaptor-kit/793rn

Those are a much better choice.

But there is one caution with all powerline devices. To work properly, both ends should be on the same electrical circuit.  If you are intending to have one end downstairs and the other end upstairs, check your consumer unit /fuse box. If they have separate mains circuits, this will limit the performance.