Pursuing Payment - Legal Advice
In the event of someone (not employed by the company) who has completed contractual work as a relief manager, it would be considered by the courts, that the brewery would not permit that individual to start work at those premises unless it was agreed by both parties, the terms by which the contract is mutually agreed. Verbal contract is also recognized in English law, although proof without a third-party witness, can sometime be a problem - unless it could be considered a 'reasonable understanding of the arrangement', based on previous example or experience.
It would also be considered in the eyes of the law, 'unreasonable', for the brewery not to pay for the contracted services, without good legally binding reason, within the prior agreed payment period - or in the absence of such 'payment period' being agreed - 30 days. beyond that period (or the agreed payment), an interest charge may be added to the account, based on current 'base rate', and charged additionally, on a continual basis.
Failure of full payment (without good legally, provable reason) would constitute a breach of contract, which can then be pursued by the plaintiff, through the courts - and can even be initiated online, using this Government website... Her Majesty's Court Service - Money Claim Online