From risk assessments, they ensure their service providers meet the requirements of the Act and have their own Modern Slavery Statement and procedures in place to mitigate risk (page 1).
Page 1 under "On-going risk assessment and due diligence process"
There are policies in place to "ensur[e] that there is no slavery or human trafficking involved in our supply chains or any part of our business", though it's not clear what ections of their business they apply to, and none of them outright condemn slavery or protect vulnerable groups.