Utilising ChatGPT for formative feedback during collaborative learning in a large class setting showed promising results. In a flipped classroom model, students received personalised feedback from ChatGPT in breakout rooms, using this to refine their work and enhance group discussions. Over 80% found the feedback useful, though its impact on group dynamics varied. This approach addressed the challenge of limited facilitator availability, providing more comprehensive feedback than typically possible. While the initial results are promising, we identified some key limitations in our activity and highlight the importance of providing clear instructions to learners about how to maximise the usefulness of the feedback provided, and to rigorously test standardised instructions and prompts for students to use with ChatGPT.