Evaluating a Workbook to Promote Autistic Wellbeing

The goal of this clinical trial is to examine the feasibility and acceptability of a brief guided self-help wellbeing intervention for autistic adults accessing UK secondary mental health services. The study also aims to begin to evaluate whether use of the workbook is associated with any changes in wellbeing. The main questions it aims to answer are: 1. Is it feasible to recruit and retain autistic adults to participate in the study? 2. Do participants find the workbook acceptable and relevant? 3. Are there measurable improvements in wellbeing following workbook use? 4. What changes, if any, do participants recommend for future versions of the intervention? Participants will: * Take part in 4-6 sessions of 30-60 minutes using the guided self-help workbook with the support of a trained National Health Service support worker, assistant psychologist, or mental health professional * Complete wellbeing questionnaires before, during, and after using the workbook * Complete brief daily wellbeing ratings throughout the study * Take part in a 1:1 semi-structured interview of up to an hour to discuss their experience of the workbook