we did some more illumination tests
and discovered that the reading is now 325lux, a drop of about 5lux after we have painted the ceiling with the Absolute White. We concluded that the finish was a matt surface and not the silk as before so we guess that Dulux was comparing the advantages of Absolute White against other Matt finish paints!
But having said all that, we also concluded that the ceiling is less harsh to look at now and gives a more satisfying glow!
We think this is well worth the drop in the brightness level of 2%!!