Hi guys I've met with a couple of block layers in lieu of starting building in months time....Two options have been presented in relation to the detailing around the windows
1 Use 3 inch L blocks returned toward outer leaf
2 Cut block and turn in toward outer leaf and place some insulation board (1-2 inchs) between outer leaf and this block piece.
The cvavity is 150 mm
The L blocks are expensive as well 1 euro a block which will add up