I wasnt clear, sorry, occasionally i DONT get the rought idle in the mornings. Please note that its not cold weather but rather starting the car when the engine has completely cooled off. The temp on the dash the other day was 14C

I havent changed the controller, wouldnt i get a fault on all glow plugs? is that something i could tackle myself? When taking apart to access,do i have to replace the gasket on the intake manifold everytime?

Was also thinking of the possibility of a stuck open egr valve, but same thing, no codes...

Injector cleaner? Worth a try?