WiFi extenders?

At the new QTH, the ham shack will be some way from the wireless router and I will not be able to see if the signal will be usable in the shack for some weeks yet; I have yet to organise the move with the internet service provider. (Reminder to self: contact supplier)  Although I could run a network cable through, I'll not do this yet in case the signal proves to be good enough.  It means drilling yet more holes in walls and scrabbling around up in the furthermost reaches of the loft, not something I want to do at my age.

Does anyone have any recommendations for WiFi extenders? Maplin and others advertise these but I am concerned about pumping data along mains cables and the resulting QRN likely to be produced, especially in the lower HF spectrum. Does anyone know of one that is electrical quiet, if that is even possible?

In distance terms, the shack is about 20m from where the router is likely to be located, but the microwave signal will have to get through 3 doors (one is metal) and 3 walls. In the current home the router is upstairs and is a decent signal in the lounge downstairs, but through one more door the signal is non-existent. Incidentally I use a recent Netgear super hub supplied by Virgin Media.