have you tried a wired Ethernet connection to see if that is more stable? Wireless is easily disrupted by a number of external factors, so a wired test is best to pinpoint if it is a wireless issue or a fault with your line or hub.
If a wired test is still unstable then try it with the hub in modem mode to bypass the router functions of the hub to rule them out as a possible cause.
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.