Cheers Martin,
I must have turned off the decals in the second file (with the ‘master’ material that has the baked bump map).
If i’m correct, the first image you’ve posted is from the second file? And the second image is from the first file?
The issue i’m trying to work out is why the bump map is looking pixelated – in comparison to the second image you’ve posted.
Here’s some examples of specific differences where a lot of bump detail has been lost after baking!
Lost detail after baking:

Detail that was there prior:
Lost detail

Detail prior

From further back, most of the bump detail seems to look alright. And ultimately it is up to me how close I position the camera when rendering.
Perhaps I’m being too ambitious, it’s just these more apparent issues that I’m trying to resolve
Cheers