Wi-Fi booster & power supply

Hi - I'm not a tech person so let me know if I'm in the wrong forum.
I'm working remotely and I want to extend the Wi-Fi coverage in the house I'm staying in.
The house is a typical 1970s, block-built bungalows, so the signal weakens the further 'back' the house you get (further away from the front hall where the telephone and then Wi-Fi modem were installed).
I'm looking at buying the TP Link AV600, which I understand uses the house's own electricity circuit to carry the Wi-Fi signal (I'm sorry for the lack of lingo, this isn't my field at all) but I've seen from one set-up video that both elements of the kit must be plugged directly into a wall outlet, not an extension cable.
Would it be possible to plug it in via a double adapter?
The 1970s wiring in the house is bearing up well but the wall outlets in the front hall are already home to a wireless landline telephone, a modem, the TV signal boost, the Eircom Phonewatch, and sundry lamps.
If a wall-mounted power outlet is a must for this item, I really don't know how it will physically fit in.


TLDR: will signal booster that relies on electrical circuit of the home work if it is plugged into double adapter