Dont use wifi to test any sort of fault - YOU MUST USE CABLED INTERNET to allow any Virgin employee to diagnose the fault.
The hub3.0 has very poor wifi penetration and distance coverage so that will just make things worse!
Try using cabled internet for a day and if its still the same issue then they can narrow it down - using wifi just makes things more complicated
because they are so many things that can affect wifi signals in your home and in neighbouring homes especially if you are in a block of flats.