Your phone almost certainly uses IPv6.
Your computer should be choosing to use IPv6 (but even Sky are flaky and the IPv6 support for the British ISPs is atrocious... Virgin don't even support it at all, but you'll get a "local" IPv6 address anyway).
Google say that something like 30% of all their queries come in over IPv6:
Just because YOU don't/can't use it, doesn't mean that it's not there to be used, or used by other people.
I bet that Sky have just given you a local-equivalent IPv6 (which is just your IPv4 inside a reserved area of IPv6) and you don't have a real external IPv6 address, or proper IPv6 connectivity, at all.
But I bet that your phone does and you don't even know it.