Quick feedback following the earlier discussions ...
I ordered a couple of LumiLife 600x600 4000K 4000lm panels from LedHut -
their fulfilment process was a mess but the panels are great. The light
is close to daylight and nicely diffuse. Because SWMBO likes a lot of
light, and it's a large'ish room, I've ordered another (despite my rant
about delayed delivery) and will order a couple of 600x300s for an area
behind a beam. In case there's too much light I've arranged to be able
to change the switching.
Thanks to everyone for the earlier replies; these panels are far better
than downlighters.