In case it's useful for anyone else, here is the template I send students when they ask for a reference. It's really useful for getting the factual details, especially when I haven't seen the student for a few years, then I can add in evaluation and specific examples.
Reference for {YOUR NAME},
I have known {YOUR NAME, a student in {DEGREE} from the University of Glasgow, since {DATE} in my capacity as their {dissertation supervisor/instructor/etc} and as a professor based in the School of Psychology & Neuroscience at the University of Glasgow. I am writing this reference about their suitability for {PROGRAMME} at {LOCATION}.
• Details of thesis title/topic or course content
• Grade on thesis or course (if known)
• Degree classification (if known)
• Any other skills/qualities you want me to emphasise (e.g., R skills, specific topic knowledge, interpersonal skills)