Last year I contacted the local outdoor ed centre about volunteering to help on DoE and other activities.
They got back to me today, asking me to fill in a form.
It is a full employment application form.
See also: Trying to get paid for a one-off anything by a university. Although that's firmly the government's fault.
Not just the UK. Son gave a one-week course in English to science students at Strasbourg university and was over six months getting paid.
Being late with invoices is I'm sure universal, but there's relatively recent change to
TEH RULEZ that mean that universities have to bring people on as full employees with background checks P60s and everything, even if they're just giving a one-off seminar or whatever. I'm not sure of the details, but I suspect the underlying logic is Priti Fascistâ„¢.