The Data Protection Act 2018, Schedule 3, Part 3, (11)
The Act has a number of schedules attached. Schedule 3 is divided into a number of parts and Part 3 in turn into a number of clauses .... so this clause reads, where the [] are mine " Article 15(1) to (3) of the GDPR [General Data Protection Regulation] (confirmation of processing, access to data and safeguards for third country transfers) do not apply to social work data to the extent that the serious harm test is met with respect to the data."
So they can process the social work data out of the UK assuming that they have passed the serious harm test.
Is this what you expected it to reference?