Alan B said:

I am coming across more curve consumer units with Lewden RCBO's in and they are causing me a dilemma.

As you will see in the picture the line conductors pass straight in front of the neutral terminal screw, the only way to check torque on the neutral is to remove the line conductors or risk damaging them.

Has anyone asked the manufacturer's advice yet? What is the recommended maintenance approach from them?

Alan B said:

So far providing the line terminals are tight I have not checked the neutrals as I believe i would be doing more harm than good

I think that's a fair point. However, it could also be argued (although I'm not sure how effectively) that, if you are loosening the line conductors to re-torque them, there's not much difference removing them and reconnecting after checking neutral conductors.

Don't let I squared r heating degrade equipment, check the tightness of all terminal screws. P.S. I do not own a torque screwdriver and never have. I have had no problems at all with that. How often do you get your torque screwdriver calibrated?

Z.

Don't let I squared r heating degrade equipment, check the tightness of all terminal screws. P.S. I do not own a torque screwdriver and never have. I have had no problems at all with that. How often do you get your torque screwdriver calibrated?

Z.

"P.S. I do not own a torque screwdriver and never have." A torque screwdriver a.k.a a Unicorn. Does anyone own one?

Back in the day, folk were taught for hours and hours of practice to tighten screws correctly, strip wire correctly, engineers to use a micrometer without a ratchet 

Precision by "the rack of the eye, the feel of the fingers" A Jedi Knight, 

Mind you, the quality of terminals was not the end product of a race to the bottom back then

Once certainly should be able to feel the elastic deformation of a (reasonably small) screw. I suspect that screws are often under-tightened. 2.5 N m needs a fairly strong wrist.

Many years ago a time-served railway fitter told me, "one, two, or three grunts" was the measure.