I managed to finish work a little early today and got on with the walls, making good progress.
As suspected, the first row was the most difficult, with the angled rebar snagging on some of the blocks. The second and third rows have been much easier, albeit some persuasion was needed in places.
I have also found that whilst the slab is pretty good, some slight unevenness does get amplified as the blocks heights increase. To compensate that I have put some small plastic wedges between some blocks to make them true again.
As you can see on the photo here, the was in which the rebar is structured in the corners is for the outside to become the inside and vice versa. I’ve used pre-bent L-Shaped 8mm rebar again for this and made sure that there is plenty of overlap (30-40cm) between these and the longer rebar that run the length of the walls (again 8mm).