Hi Jimmy
I was listening to the podcast and you mentioned being curious about the 2mm rule. I could only think they were quoting from The Guide to Standards and Tolerances:
However, item 10.14 would imply over 1mm is defective.
10.14 Cracking in plasterboard, hard plaster and other plaster elements
Cracking in walls, ceilings and bulkheads is defective if it exists at handover or exceeds 1 mm in width within the first 24 months of completion and can be seen from a normal viewing position.
Cracking in recessed and butt joints is defective if it exists at handover or exceeds 1 mm in width within the first 24 months of completion and can be seen from a normal viewing position.