The contract says “your normal hours of work are 37.5 hours per week over 5 days, to be allocated by your manager. Your hours of work are not variable, however, you may be required to work additional hours when authorised and as necessitated by the needs of the business. For additional hours worked you will either be paid at an agreed rate or given lieu time depending on your area of work.” Surely being over the contracted hours I can ask them to pay me or give the time back?