After 10+ years of decent home wireless coverage, about 2 months ago signal seemed to 'collapse' overnight. Now need to stand almost right next to the router to get decent signal. Zero chance of picking up wireless signal upstairs
No issue with the PCs/MACs that are hard-wired back to the router.
Seems impossible to actually speak to anyone at Virgin
Wireless reception is affected by many factors like Range, Client hardware, the Topograpy of your home, and the big killer, Wireless interference.
It could be a recent nearby source of wireless interference such as a neighbours baby monitor, a car parking outside with a wireless car alarm for example.
You could try changing the wireless channel manually. Downloading a wireless scanner like InSSIDer for Windows or WiFiAnalyser for Android would help by showing you the surrounding wireless networks, the channels they are broadcasting on, and their signal strengths, so you can select the best wireless channel.
Setting the Hub's radio setting to 300Mbps (or 40Mhz channel) is not advised on the 2.4GHz band as it takes up over half of the available spectrum, making it prone to wireless interference..
I would also check for other sources of wireless interference such as A\V streaming devices, Baby monitors, Chordless phones, Microwave ovens, Plasma TVs, Security systems, etc.
Using the wider, usually less congested 5Ghz band could help, if your client devices support it.