As an European Economic Area student, you can work in the UK but However students from countries like Croatia might be subject to the Worker Authorisation Scheme.

How many hours you can work and the kind of work you can do depends on your visa status and where you study. Most International students come to the UK to study with a Tier 4 visas which can enable a student to work while they are studying in the UK.
Many students can work up to 10 or 20 hоurѕ durіng tеrm tіmе аnd full-tіmе durіng hоlіdауѕ, dереndіng on your study level

A student with this kind of visa are allowed to work during their studies and when they are on holidays.
Also, a student can do a work placement as part of their course, but are not allowed to take up part-time or full-time job in the UK if they are publicly-funded.
It is mandatory for students to check if their visa status will allow them to take any job or internship, please check that your visa status allows you to work in the UK, and if so, how many hours you can work per week.
You can contact us to help you with further information.

Just as you have it in USA students who complete a degree program in the UK are allowed to apply for a 1year visa extension without having to obtain a work permit this is to allow them to gain work experience in the UK.