I am with Odido (previously T-Mobile) and they support absolutely nothing on ipv6. “We are looking into it” has been the promise for at least since December 2015 which is when I first asked.
The situation with one major ISP in the U.K. is so chronic that someone even maintains a WWW site tracking its patent inability to progress any further than where it was on World IPv6 Day:
A Virgin Media door to door salesman called a few months ago, trying to get me to switch. I asked if they supported IPv6 yet and he said “yes we do! and Netflix and Apple TV!”.
It is sad.