I suspect that a business is paying its employees less than the minimum wage. What action can I take?

I was shopping at a new improved branch of a certain company I used to work for, which I shan't name, for obvious reasons, and I got talking to an old colleague of mine. He claimed that employees his age (20) were getting paid below the minimum wage. As this company pays by length of shift, he told me that he... show more I was shopping at a new improved branch of a certain company I used to work for, which I shan't name, for obvious reasons, and I got talking to an old colleague of mine. He claimed that employees his age (20) were getting paid below the minimum wage. As this company pays by length of shift, he told me that he was getting paid £17 for a four-hour shift, which works out at £4.25 an hour. As my mother works in payroll (for a different company) I am pretty sure that the minimum wage for his age group is way above this (at least £5.00 an hour).

Also, this same company has 6am start times, due to deliveries, and one employee, who is under 18, was given a shift starting then, even though I have been informed it is illegal for under 18s to work before 7am. Is there anything that the person in question could do?

P.S: Whilst I appreciate answers from any country, it would be helpful if people from the UK could answer, as I know that there are differences in laws everywhere. Thanx 4 input!
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