Some general notes: Bectu offers a course on working regulations and policies designed to protect the child at work. This is a City & Guilds accredited course offering a practical guide to everyone working with children in the entertainment industry. You will gain a sound understanding of the DfE regulations, as well as the Local Authorities licensing processes.
The HSE website has a useful page on what the law says about young people at work. It makes the distinction between ‘children’ and ‘young people’ (defined carefully on the site).
There’s also a useful printable guide [pdf] here.
The FAQs are also useful, and doing a risk assessment around issues relating to children/young people seems central to it.
There are specific rules on working hours and pay for young people at work on work experience on the Acas website here. In essence, if what you are doing amounts to work (even if you are volunteering) you are entitled to the relevant statutory minimum wage. If you are only shadowing, you would fall on the side of not being entitled to the minimum wage.
School students on work experience aren’t though, and neither are HE or FE students doing less than a year of work as part of their course (though they often actually are paid).
If an employer has someone volunteering, they would have to show that the volunteer is not actually doing work (so not substituting someone who would be doing paid work).
The National Careers Service has a useful page that explains work experience.
There is something on the .gov website about Chaperoning but a lot of the responsibility for this seems to rest with local authorities – an issue that (on the face of it) seems to result in inconsistency. This is an issue that the Bectu Chaperones and Tutors Branch has talking about for a while.