To edge the raft, below floor level, I would use engineering.
o Standard blow off in hard frost, damp, in sheltered area
o Standard blow off if any roof/guttering leak in a hard frost
I know the latter from experience and Warrington imbeciles
who fitting guttering with more leaks than it had originally.
If you have to replace a brick it involves Armeg chisel each
one out, mortar in a new, one by one, over a period of time.
Concrete block is probably acceptable, but are engineering
that much more for 3 courses - it should bluntly be bugger all
cost compared to the price of a raft (which is vastly more).
Standard bricks can be as porous as a sponge.