@shamus1's question seconded.
HH5 was meant to have been enabled for IPv6 "early in 2017". We're nearing the end of April now and still nothing, so in no way is this in the spirit of what was announced as being the IPv6 plan. (The jokes about it meaning the last day of June were funny, but the actual situation isn't funny at all for HH5 owners who believed in BT's statement.)
I suggest that if the official plan has slipped, then there should be an official update about it.