On Value Fibre, which unless you turn the modem off is always on, presumably the dynamic one only changes with power cuts, so perhaps not too important. Or is it sticky anyway?
tbb QM being the issue.
In my experience Plusnet IP address are VERY non sticky, they change every 48 hrs or so.
It's a pain, because I've just migrated my parents over to Plusnet Value, and set up DynDNS, but that's still useless, because their router (Netgear 834) only refreshes the DynDNS entry on reboots !
My mother in law's Cisco is fine, DynDNS refreshes within seconds.
However, in neither case can I use the TB BQM sensibly of course
Oh well, live and learn !