Check the badge in the driving instructor’s windscreen – if there isn’t one you should not take lessons in that car! The person sitting next to you might be pretending to be an instructor. They could be anyone.
A green octagonal badge shows the instructor is fully qualified and an ‘approved driving instructor’.
A pink triangular badge shows the instructor is not yet fully qualified, but undertaking practical training.
They are allowed to charge you for driving instruction but bear in mind that they are still learning and using you to practice…