> However, service workers have wage pressure to sign waivers to let them work more than the 48 hours
US wage and hour laws are not generally individually waivable, as the entire point of wage and hour laws is to address power imbalance between workers and their employers. When talking about the length of the legal workweek in the US, the discussion is of laws as to when overtime compensation for non-exempt employees is required, the added cost creates pressure on employers to limit excess working hours of non-exempt employees.
If UK wage and hour laws are waivable the way you suggest, that suggests a fundamental problem with the structure of the law which renders any discussion of fine tuning their coverage irrelevant.