I recently took a call from Virgin offering a 'free broadband assessment' at my home. I said yes as I was a little disappointed with the reliability of the wifi around our house. The engineer was great; he identified the problem (my Superhub 1 was broadcasting on a congested channel in the area) and fixed it by configuring a Superhub 2 to use a less populated channel on 2.4Ghz and also activating the 5Ghz signal too. Instantly I was seeing speeds, during daytime at least, of 150mbps on all devices.
Sadly though, the wifi on the Superhub 2 proved unreliable, and a glance through various forums suggested that it's a very common and known problem with the Superhub 2 that the signals can drop for no reason. The solution is to either ask Virgin for the newer Superhub 2ac if you have devices that can take advantage of 802.11ac (ie from the last 18 months or so) or to add a 3rd party router.
I've now added the Apple Time Capsule, which centralises backups for my whole house (we're exclusively Apple) and the wi-fi has been super reliable and blisteringly fast across the board.
I post this as it may prove useful to others struggling with Virgin's wifi, but also to ask a question: why do Virgin undermine the promise of their class leading broadband by dishing out sub-standard hardware? Surely that's self defeating, and good routers are cheap as chips these days.