What starter bars?
You can't use them with double brick unless you core filled a cavity and made it wider than 230mm
I'm pretty sure a slab rebate isn't required if the wall is being waterproofed.
Speaking of which, good luck to them in doing that without someone spending a day on the shovel.
Lets just hope the vapour barrier that's folded up is still in good nick
Waterproofing retaining section of wall will stop ground water. What about the top of wall subject to driving rain? Where will the water go if you don't have a rebate? Straight back into garage.