Lower brick course separating along a 2 - 3 metre area of external wall.

[Mr Punter]

Well that all sounds good.  It is far better to check and know for sure, rather than worrying later when you have committed yourself.  The path should really be 150mm lower than the DPC but if it has not caused any issues it will be fine.

[Brickie]

Inner leaf blockwork is standard,and likely would have been at the time of construction. The mineral wool is probably the insulation installed as it was built,the beads are more likely a retrofit (or possibly an annexe extension?) 

Possibly installed by lifting the bottom course or two of roof tiles to give access to the cavity,and hence no tell tale holes. 
All just speculation,of course?

Edited October 21, 2021 by Brickie
Typoo

[dssr]

So mineral wool at point of construction in the 60s would have be forward thinking?  No extension, all four walls are the original footprint, so weird how they have mineral wool on one side, and beads on the other.

 

Any reason why the inner leaf's are blocks at the gable end and brick for the sides?

 

Not a concern, more a curiosity.