Well this is interesting...
I have tried rebooting my Smart Hub several time over the last few days and still no IPv6 issued.
Anyway I just brought myself a FRITZ!Box 4040 Router, which is basically only a router and has no modem.
This comes with a 1Gbit WAN Port and 4 1Gbit Ethernet Ports and a couple of USB2 and USB3 ports and that's it.
Sadly this model isn't for the UK hence it only comes with the standard 2 pin European plug on the PSU.
Lucky I already had a FRITZ!Box 3390 ADSL/VDSL Modem / Router that came with a UK plug on the PSU, luckily it was the same voltage and polarity but with a higher power rating which helps.
Anyway after I configured everything up, turned off features I didn't want and nail it down as secure as possible, I noticed that IPv6 was working again, I was like BT must of fixed the issue, so I thought I would try the Smart Hub once again, sadly no IPv6, so a few more reboots and still no IPv6.
Connetced up the FRITZ 4040 and IPv6 was enabled, did several reboots etc and every time it had IPv6.
So from that conclusion I am thinking BT's IPv6 issue must be an intermittent Smart Hub issue that has a hissy fit with BT's DHCPv6 Servers.
I have stuck with the new 4040 due to its not sluggish at all even when connection is at full load which is good, it also comes with a great Wi-Fi Scanner to see what channels are in use and how many are using them.
This also means I can have the BQM running on my connection now where as before with BT's Hubs I haven't be able.
I might use the Smart Hub as a Wi-Fi point at the back of our home.
So overall its a win win