It has always worked so well on the iPhone I’ve forgotten how I did it.
For some reason my Gmail (custom domain) works instantly in the iPad, I’ve forgotten how I did that already!
But I am now setting up the Google (Custom Domain, apps docs, whatever they call it!! – How about Google Live? Google Cloud? Google Everywhere? To hard to name: Gapps?)
Short answer, worked instantly:
Maybe this that I had already tried
had a part to play.
Anyway it works
The MS Exchange way did not, however I had to get my Contacts working using MS exchange.