Hi there!
Firstly, I wish you the best of luck during your application / interview, and congratulations for getting shortlisted for your course! In my opinion, Social Work courses are one of the hardest to get onto (purely due to all the written tests / exams / interviews beforehand!)
I am a final year Social Work student, and I have just had my first interview for a qualifying post. Unfortunately, I was unsuccessful for the position - however I did receive detailed feedback!
When applying to University, I was required to do a group exercise on a case study of a service user, saying amongst the group how we could assist and help provide the support that the service user was requiring at that time. We were all scored on our group performance, and how well we worked together as a collective team. From memory, the groups were split into 7 to 8 people per group. Next, we had a 45 minute written exercise. This was conducted in exam style conditions, and as other users have mentioned above me, centred around the interventions of a family and how to approach them / begin to conduct an assessment. Finally, we had an interview with a practicing social worker and a member of teaching staff, who asked us an array of questions and related it to the 'First Level of the Student Descriptor of the Professional Capabilities Framework' (this document is available on Google if you would like to type it in!) - to assess our values, past experiences, and our reasonings for wanting to become a Social Worker.
When I recently had my interview, the Assessment Centre followed a similar style of formatting.
I wish you the best of luck, and please do keep us updated with how you do!
Kind Regards,
Freddie Mercury Fan. (Freddie _ Mercury.)