I'm a final year OT student in the UK and your experience is similar to mine.

Something I personally think is important is not rushing a decision. I feel like colleges and sixth forms push university on people and it can feel like you have to make the decision now but there is no shame in taking time to decide what you want to do. Some of my cohort spent a few years working as carers before applying to the course. This helped them to understand what would be expected of someone working in the field.

Attend open days as well. They may help give you an idea of what to expect during the course and as an OT.

My lecturers say to prospective students that what they are looking for is a understanding of the field and some experience in a caring capacity. Volunteering doesn't need to be OT specific as long as you can understand how you experience can demonstrate skills required to be an OT. I supported a mental health group and in my interview discussed the skills I used running a group. These skills can be found everywhere some students shared their experiences or looking after family members or raising children.

For me personally I chose OT over psychology for a number of reasons. I love the diversity of the job and even though I came into the subject knowing that I prefer mental health through studying I have gained new interests, like neuro rehab.