can you paint over an artex ceiling with white paint without it going yellowy. I was told it was meant to not be painted but ours has a sheen and I thought a matt paint might tone the pattern down?
There's no problem painting over Artex. Many paints are now 'non-yellowing' - it'll say so on the can. I use B&Q 'Everwhite' matt and get good results. Of course, any smokers using the room will yellow the paint anyway.