Sorry I have no solutions for you ProfWilbur but this sounds like exactly the same thing that's happening to us. Internet itself is ok, but wifi cuts out intermittently for a short time, then comes back up again, several times a day. It can be fine for weeks, then starts again. It's also happening with our neighbours down the road, also on Virgin.
There doesn't appear to be any reason for it (we've also had multiple hubs and the engineer out many times) so must just be some weird wifi interference from some other device in the area that virgin boxes don't like.
In my view the chances of Virgin sorting this out are very very slim. I think our options are 1) wait and hope it sorts itself out 2) buy different wifi equipment and just use the hub as a router 3) change providers completely.
As we're lucky that we can use ethernet for important devices (tv and work computer) we're going for 1 at the moment!