ok - an update. I ran out of white primer and ordered some grey @Gareth Hughes. However many trenches, bangs and scrapes I fix, there are always more, grain filler doesn't touch them. I will never buy paulownia again.
The grey made a good job of covering and I have now decided to top coat and live with it (the front isnt too bad and I am confident that I can overfill with paint and flat down) . I had sprayed a test swipe of olympic white on white primer and it was a bit pearly as noted above. I've now done a quick mist coat all over the grey and am pleasantly surprised (a first for this endless viking saga of a build) that it looks a very mellow white.
picture added @Gareth Hughes
Should go nicely with the celluloid brown tort that I have waiting. @vinorange