Mind if I ask who you have dealt with at Nationwide? I too have an order with them for ST 4Drive.
Chris Hodgkinson is their Seat specialist who i ordered through.
After placing the original order I e mailed him once and he politely told me when they have an update then it would go on their system and I would get an e mail.
A few weeks later I e mailed again asking some other questions and he never bothered himself to reply.
From that point I thought, "sod it i will just leave it and see what happens" (fortunately I have a car to use in the meantime and so am in no rush to receive it) If they turn out to be useless, I can always just cancel it and get my brokers fee back due to unreasonable delays so nothing would be lost.
I then received an e mail update on 2/8/18 with this provisional build week, this is all it said nothing more.
This is where i am at, when they give further updates and it gets nearer the time i will say i want a 19 plate please which I feel is reasonable.