Regarding cadetships/internships, I believe you need to think about it in the sense that you are technically applying for a particular role. In the case of normal positions, qualifications such as your education and your work experience will likely be considered. This will of course depend on the seniority of the position where, for instance, a senior role may emphasise the need for substantial work experience in the field. In the case of a cadetship, your academic position is likely to be emphasised. This means that, in order to maximise your chances of securing a cadetship, you must ensure that your performance (results + WAM) are of high standards, potentially making you a more suitable applicant due to the possible advantage gained from optimal performance.
With that being said, while the focus is on your academic performance (since you will be a university student), having prior work experience definitely remains encouraged and can be advantageous with respect to your chances of securing a cadetship as it strengthens your application and hence makes you a more competitive candidate. Having prior work experience is also beneficial and can be utilised during an interview stage to answer behavioural interview questions in an effective manner, particularly common ones such as:
- Tell me about a time when you handled a challenging situation.
- Tell me about a time when you made a mistake.
- Tell me about a time when you were in conflict with a peer and how the situation was resolved.
- Tell me about how you work under pressure.
I hope this helps!