The only place to access my brake bias bar is via the top of the pedal box. This has a cover over it. If I lockwired the cover, would this satisfy IVA note 5 (below)....Yes, I know, a bit of a long shot, it's just it will avoid removing my brake pedal again.

Note 5:
Bias bars and other mechanical adjusting devices fitted to twin master cylinders must be rendered inoperable by mechanical means
e.g. lockwiring of components.

I thought the reason for lockwiring was to prevent movement while driving, not just to prevent alteration. Lockwiring the cover wouldn't stop the bias bar from moving under vibration.

It's not to stop movement, it's simply to stop adjustment.

Nope - it's to prevent movement. I had TWO, yes TWO nylocs on either side of my brake bias bar. I failed my IVA as I had no lockwire / split pins in them.

I suspect this interpretation will vary between inspector. My impression (judgeing by the requirement to add the note about adjusting it invalidating approval) the RS was to do with not allowing adjustment. However It could be for both. Call the centre to see what they expect to see.
My feelings are the wording is 'components' need to be lockwired, so will not cover the access panel.