You don't have to use FL if VFR
What you probably mean is "you don't have to fly at a rounded FL according to the quadrantal/semi-circular rule" if VFR.
But as far as I know you have to use flight levels in your reporting to ATC, if you're above the TL. I mean, you don't want to leave the mental arithmatic to the controller, do you?
"G-ABCD report altitude" "6200 feet QNH 1003 G-CD"
"G-DEFG report altitude" "FL65 G-FG"
Now is there a conflict or not? (And what's more important: How many seconds did it take you before you found the answer?)