Moved to virgin from sky and not liking it one bit! The on demand and catch up service is terribly slow bit I can cope with that what we are not coping with to well is the Internet connection... as soon as I go up stairs my phone won't load anything and the WiFi signal is very low. There's nothing blocking the modem and I've tried restarting it...it's the same if I go into another room it's shocking virgin you need to sort it out!!
Wireless is easily disrupted by a number of external factors so it is not something VM can control or guarantee, no ISP can. The VM hubs, like all free ISP routers, are basic devices that for some people are fine but for others not so much. The only thing VM will suggest is trying different wireless channels, they have a guide here.
One option might be power line adapters. These use the electrical wiring in your house to create a wired network without the need for long cables. They are rarely as fast as the manufacturer's claim but are a lot more stable and less prone to interference than wireless. Some provide just wired connections and others come with additional wireless built in to allow you to create a wireless access point in parts of the house where the wireless signal is poor. Some powerline adapter reviews here: http://www.pcadvisor.co.uk/test-centre/network-wifi/20-best-powerline-adapters-2016-uk-3490638/
Another option to improve your wireless is with a third party router. It is what I and many other customers do and it can make a huge difference.
Disclaimer - I don't work for Virgin Media. I'm just another VM user trying to help out so my answers may be wrong If my answer solves your problem please mark it as helpful as it may help others My setup: Vivid 200 Optical fibre with Superhub 2 in modem mode connected to a Netgear R7000 router. Telewest/VM user since 2001.