Not paid for shift on Nov. What are my rights?

[Octopuscrazy]

As titled. Did an additional shift for my employer in November (NHS). I STILL haven't been paid for it despite chasing multiple times. What are my rights? Next steps?
I have escalated several times to the manager. She says it's on the "bank" (which is like the department that pays these shifts) to pay and she will chase but nothing has happened yet.
Do I send an invoice? Can I add a late payment fee?
Thank you

Submit a formal grievance. That is how you escalate disputes with the employer. Taking them to court will take far longer.

Definitely a formal grievance but I would also think about the wording and set it out as a formal request to be paid by x date. This way you would also have the option to issue a letter before action if you haven’t been paid by x date. So you essentially have a grievance and a potential small claims case running together.