BT promotes guaranteeing WiFi in every room. I've called Virgin on plenty of occasions and the only thing they do is say I need to reset the router. Is BT's hub much better than Virgin? Is there guarantee to have WiFi in every room no different from a home plug set? Or all this just marketing talk?
I don't know what BT's offering is, but one suspects it's either additional Wi-Fi Repeater(s) and/or some kind of "whole home" or so-called "mesh" systems which is basically a fleet of Repeaters that employ some additional automation to do things like set up the channel plan, steer clients to the "best" AP, pre-stage some of the roaming hand off and so on. However, without seeing the spec. of any particular offering I couldn't say.
What I can say is such systems don't possess any voodoo that generates some kind of magic "different" Wi-Fi trasmissions than everyone else's - it's all using the same Wi-Fi standards and has to obey the same laws about transmit power (albeit that there is a huge variety of "options" in the Wi-Fi standards, so there's plenty for any vendor to choose between in what they include or omit.) There's some clever stuff that can be done with antenna design and phased arrays, but you generally find that in after-market kit and pay for the privilege. Even then, it tends to achieve better "rate at range" (speed in a given location) rather than any radically large coverage area improvements.
I'm not quite cynical enough to think this is all just "marketing hype" - I think it's more that the ISP's are recognising that "one AP in the middle of the house" doesn't cut it for increasing numbers of people and they are bringing forward multi-AP solutions to address this and appease their customer base. IIRC they gifted one of my relations a Repeater (A Repeater is effectively a Wi-Fi AP that uses Wi-Fi to estabilsh it's backhaul link to another router/AP.) What we are seeing is the percolating down to the SOHO realm of something that enterprise Wi-Fi builders have known forever - if you want good Wi-Fi coverage and performance, you need lots of AP's deployed as near as possible to where we expect the the clients to be. The "hard" part is the backhauls as discussed previously.
Unfortunately comparing one locale to another is pretty meaningless when Wi-Fi planning. One just has to be a bit "zen" about that and accept it. Sometimes with some of the best planning tools and expertise in the business, when we turn it on it just doesn't work how we thought it would and we have to investigate and find a solution. Wi-Fi, I'm afraid, is "just like that" - there's no silver bullet product that's guaranteed to work every time every place. Though plenty of us "in the busniess" have our favourites.
By way of example, I live in a very modestly sized property of about 40 square meters and have only two Wi-Fi devices and that should easily be serviced by a single AP (built into my router.) But to get from my bedroom to my router entails 4 (stud) walls and a bunch of water tanks and it's lousy. So I've got Repeater half way between the two. Worse still, I live in flats and as such have to compete with all my neighbours Wi-Fi as Neil has discussed, so there's no chance of me finding a (radio) "channel" all to myself and we have to "play nice together." It'll work fine for weeks then for no reason at all someone's router will re-tune itself and the whole lot falls to pieces for a few minutes. Again, unfortunately, Wi-Fi is "just like that."