When can they bring a solicitor to a disciplinary meeting?
When the consequences of them being dismissed would mean that they could never work in their profession again. Ever.
The best example of this is a real case where a secondary school teacher was being investigated for inappropriate behaviour with a pupil. If the teacher was dismissed for that reason, then he would never be able to teach again and would have to do something entirely different. The Court of Appeal ruled in this case that it was fair and reasonable to allow him to bring a solicitor to each disciplinary meeting. The consequences of a dismissal based on hearsay and not rigorously tested proof would have been calamitous for him.
The same would apply to a medical professional or even a care worker in a similar situation. But it doesn’t apply to 95% of the employees we deal with.