Guys, thanks for your advice. OW lamp is coming on at around 2bar as you suggest, am reasssured to hear this is fine at idle, just can't explain why the OP stays that bit above 2 when the level in the tank is higher.
Dave, I think I confused you with my "downwards" comment! I didn't mean that I get more ejected at lower levels, just that I have not yet found the point at which it stops ejecting...
I will ignore the OP light at idle, hold off topping up, and see if the level stabilises a bit lower down in the tank....