As far as I know, there is no requirement for labourers to hold a CISRS labourer card, but it would be preferable. CSCS as a minimum, with manual handling training essential. According to NASC guidance - 'Labourers are only allowed to work at ground level or with safe access to a fully boarded and double guard railed section of a scaffold platform passing scaffolding equipment.' Is it only an advanced scaff and labourer on site? What is the type of scaffold work taking place?

These 3 labourers must not wear harnesses or carry tools, as their role is only to move materials around (poor buggars!). They can only ever access completed sections of scaffolds - fully boarded and guardrailed. As long as your advanced scaffolder can complete the scaffolding task safely single-handed, you should be okay. Then there's the other stuff to consider : rescue, scaffold design, material quality, PFPE use, etc. Probably all covered in their RAMS if they're a decent outfit.