Harry Bloomfield wrote:
I told breeze block is quite suitable for outdoor use, can anyone
confirm this is the case and/or advise on an alternative light weight
building block?

Its a small shed.

Concrete should be OK, I certainly would not use breeze
blocks or aerated where it may get wet (and worse: freeze
wet). You could use them above DPC with a good layer of
waterproof stuff - timber, corrugated iron, cement render
with waterproofing admixture - but...