Turns out that my cards stock speeds are actaully 555/500/1350 and not as i originally posted
I tried to push it to 630/530/1565. it ran ok on a ntune stability test however when i ran Skyrim it didn't like it at all.
Took it to 600/500/1500 and it seems to be fine.
A bit higher than my stock but not too bad.
i am happy. Will do me until i get a GTX 560 OC