OK, sorry...never mind - I found the problem in my outdoor terrain test.
Although my graphics card driver was only 1 year old, when I updated it fixed the problem and so left me with basically the same graphics as in the editor.
I found Antialias at 2x (333 FPS) was best, as 4x (250 FPS) only had slight difference and big FPS drop (from very high level).
Everything else at max settings was fine except Anisotropic filter ran better switched off strangely for outdoor terrain environment...