They've been looking at this for a while. In common with other smaller operators they've been waiting for the national product.
Be interesting to see if they pull the trigger. I can't say I really get the point of A&A over FTTP but obviously mileage will vary.
"Hello you are through to Wendy at BT support"
"Hi I noticed my ipv6 prefix changed, I thought IPv6 addressing was enough to avoid this nonsense"
"Sorry can you repeat that"
"Sure ..."
"Ok please go to your home hub, and look for the button with this ... symbol, press it, then wait 5 seconds, and press it again, this should fix it."
After escalation.
"Yes sir, we cannot manage our network in a way to give static allocations, so your prefix will change from time to time, also please dont bother our agents with this, if you can reach google, the service is working to an adequate standard".