Cheers for the feedback chaps. I had a response from light-bicycle ..
The brass nipples will be better.
We do not use the washers, but, if using, it will be better.
For spokes tension please find our reply as below:
A. Tension for "transportation riders" (Comfortability)
80-90kgf are ideal for regular transporation riders or exercise on a regular basis.
B. Tension for "enthusiast riders" (Balance)
100-110kgf are good for people with enjoyful and training purpose.
C. Tension for "professional riders" (Performance)
120-130kgf are charged for riders who are expertized in riding or competition.
the recommendation spoke tension is less than 130kgf..
So they're pretty non committal. Basically it "would be better" to use Brass and washers..
I'm certainly going to go with the brass and I'll see what the wheel builder thinks about the the washers. I'm not overly fussed on the lightness I just want a stiff wheelset that I can depend on.
Fingers crossed I've made the right decision