Under the Working Time Directive (which applies to most workers and sets out the minimum standards for working hours), your employer has to offer you a break of at least 20 minutes if your working day is longer than six hours. However, there is no requirement under the minimum standards for your employer to pay you for this break or to count it towards your working day.
If you're 16 or 17, you get more generous breaks. You’re entitled to an uninterrupted break of at least 30 minutes when you work for 4.5 hours or more.
Check your employment contract, as there may be arrangements for longer and/or paid breaks where you work, especially if a union is recognised at your workplace.