If you need uptime then get a backup connection. Virgin Media's business cable modem service is just as susceptible to faults as their residential one (because it's the same network), and you don't get the compensation for loss of service with the Business products that residential customers would receive. It's also very difficult to have your address flipped back to a residential one if VM tag it as a business.
The tech support is equally bad regardless. The 12 hour resolution time is a target, not a guarantee. If they miss their own target they pro-rata refund you, which if you're paying £60 a month will be £2 a day. It's barely worth having.