Thanks heaps for your replies, very helpful. I'll spend the bit extra and core fill with concrete to get the best result.

Thanks Stewie. I have started laying the blocks with mortar. Could I leave cavity in blocks empty or fill with soil? I will be putting capping tiles…

I am building a besser block wall 3 rows high (600mm) and 5 metres long. I have poured a concrete footing have put 600mm upright reo bars in each…