Service Void battening on blockwork wall

[crispy_wafer]

Amongst this weekends tasks I intend on battening out a block wall for a recessed consumer unit and some service routing. 

 

Should I frame the wall, like a stud wall with horizontal header and footer, or is it simply ok to install verticals every 400 top to bottom? 

Also, is it worth insulating the voids, whilst avoiding the cable drops to the CU?  Construction is brick and block with a full filled cavity.  Should I add strips of dpm to the backs of the timber and should I paint the blockwork with airtight paint (got some soudatight left over)?

 

Thanks

Marek