Virgin are not very good at customer service and if your service works well then it is very good, if you have problems well that's another story.
A few things to note
BT have to provide you with service anywhere in Uk Virgin do not so they dont serve private roads remote locations, long driveways. My neighbour had to build his own duct from the adjoining street to get Virgin and doesnt reckon it is really worth the effort compared to BT who themselves are starting to roll out Fibre to the home .
Are speeds over 100Mbs really worth it for domestic users , perhaps in a household with 4 teenagers and mum and dad homeworking it is useful but as outlined above maybe in 5years time 500 Mbs might be required for heavy users.
Fibre optic cables do not degrade which can happen with copper but they are just as easily cut by wayward digging , trenching , street works etc which are one of the main reasons you might lose your internet.
Equally they are no protection against equipment faults in your nearest network node(telephone exchange)
So, a few things to think about value wise before just going down the if its faster it must be better route. Rather like digital cameras, 20Mega pixels is better than 12 but the eye cannot tell the difference, unless you do lots of large scale enlarging the images both look the same