What are my rights if my hours are cut via fire and rehire?

You have the legal right to refuse the change, reject the inferior contract, and file a claim for unfair dismissal.

Unilaterally slashing your hours by firing and offering to re-engage you on a reduced schedule is a direct breach of employment protections. If your employer attempts this, The Workers of England Union will immediately step in to represent you. We will challenge the breach of the Statutory Code of Practice, aiming to secure both an unfair dismissal ruling and a substantial "Protective Award" uplift in compensation.