Okay I've got two suppliers BT with ipv6 and Virgin ipv6 will arrive eventually in a bodged format or when ipv7 comes out. i.e never.
I've got ipv6 running on my home network.
I've got some pc's with all the traffic going via virgin on ipv4 and some others going via BT mainly my web cams.
Sometimes this causes a little confusion on pc's on the virgin network because ipv6 is of course BT's. This normally when 3910 has a fit and stops resolving IPV4 and you end up with some sites working and others not as they don't support IPV6
Would I be best just turning ipv6 off or just use ULA for the home network until either Virgin does go IPV6 or BT upgrade their system at which point I'd may well ditch Virgin altogether.

I'd ask DrayTek to fix any problem with resolving IPv4... but resolving..as in DNS? Surely your PC is doing that bit ?

Nope it was a bug in draytek firmer which seems to be fixed now.

Pc's can't resolve dns if the router has ceased passing ipv4 traffic.