More broadly, I think home desktops are getting rarer in the UK. Wifi is the obvious answer for portable devices with wifi capabilities built in, even in dense housing with lots of devices interfering with each other.

Powerline networks are mainly utilized by people living in concrete multi-story houses that either do not wish to install a proper Ethernet backbone to all rooms or take a gamble with WiFi due to higher cost, thickness of walls or other reasons that might seriously affect connectivity as mentioned before.

I used to run my own IT support company with several employees (think Geek Squad) having both enterprise customers aswell as private sector and people running Powerline is actually a lot more common than you might think (my parents for instance are running it along with WiFi in their house - deskop, IPTV and camera surveillance is on Powerline while tablets and phones are on WiFi).

During all my years in IT I've encountered two situations which I can remember where WiFi was used on a desktop machine instead of Ethernet or Powerline - one was a car dealership where they had a salesman sitting in a "glass box" and they were sharing building with another company (so, no Powerline) and other situation was a enthusiast that built himself a new computer and his new Asus motherboard came with 802.11n built-in..

Personally, I am running all my desktop machines on a 10Gbit CAT6a network I have at home (I do have a WiFi as well but it is on another VLAN with no access to network infrastructure - mainly used by kids) where I have possibility to stream multiple 4K streams from my FreeNAS server while downloading huge files of the Internet without even breaking a sweat - try to do that over a WiFi connection and you'll hit into a brick wall pretty fast.

Most people when buying a new house can stomach (not sure why, because it can't be a large portion of the overall cost of a new house) multi-line pulls from each room to a central wiring closet. Plus, you have to have that central closet (or panel at a minimum) somewhere out of the way, and most people just don't get that kind of tech (the idea of a central area for a home server, plus networking stuff, etc).

So - the lines aren't installed (at one time, houses were offered with the option, and if you are willing to pay today, you can still get it - but most people don't). After the fact retrofits aren't done because such an install is very difficult to do (especially in modern houses with horizontal firebreaks between the verticals, little to no attic with vaulted ceilings, etc) - which also means its expensive.

So instead, people go with wifi. It's cheap, no need for a dedicated wiring/network termination panel and/or closet, and can be taken down and taken with you if/when you move.

Personally, I prefer a wired system; when I moved into my house I installed a few drops myself where I knew there'd be some dedicated hardware (TV area, my office, library, and my shop); the other rooms I never installed anything because it didn't matter. For those, the wifi I have fills in those blanks adequately. I ran all the lines back to a custom wiring closet I built in my shop, and terminate everything there (plus a few of my servers live there too).

Now in a house I see maybe 10 APs and they are all at the edge of their range and I rarely need to tinker with it and it works all the way across the street.