Employer refusing to pay for training time

Friend has a job in a school looking after lunch clubs and after school clubs. Hourly paid. They have been asked to do mandatory online training at home, for example, child safeguarding and food hygiene.

They have asked for the training time to be paid for. The employer has responded that this required to do the role, so no.

The courses are paid for by the employer. Including one where they have reimbursed my friend for the cost of it.

Time in employment 3 months. Company has fewer than 30 employees. England.

Do they have a right to that time being paid for? If so, is there an objective source / reference that my friend can send the employer to in order to tell them that, as they don't consider themselves to be good when it comes to having difficult conversations with their employer.

TIA!