The full sermon is available as a video, here (27 minutes).
The context of this event is explained here.
Lambeth Palace has issued this press release: Archbishop Justin visits Nairobi.
The Church Times carries this news report by Madeleine Davies New structures needed, Welby tells GAFCON Primates and this additional commentary Archbishop and Gafcon Leaders size each other up by George Conger.
There is also this report by George Conger Welby backs GAFCON vision for a renewed Church which says there were some changes made to the sermon at its second delivery.