Vodafone have a first come first served contract with Huawei... Which means Voda get everything first.... When the Mate 10 Pro landed.. Vodafone was the only company who did it before 3 and I think EE, even before Carphone did it unlocked ... O2 dont do the M10P...
So the secret is... when you buy a Huawei phone in the UK, put a Vodafone sim in on out of the box boot up... Let the device download Voda settings and IP.. Do the updates, then hard rest and put your own network Sim in...