Just been undertaking a review of a company's furlough calculations. For hourly employees, contract of employment states that hours over 35 per week will be paid at time and a half, and that Sundays will be paid at time and a half.
For flexi-furloughed staff, the agreement simply states that they will be paid their normal rate for hours worked. It was widely accepted by staff that they'd not be getting paid any overtime hours (i.e. at time and a half) - during the flexi-furlough period (i.e. since last July), they've not been working more than 35 hours per week. Seems to me though that, strictly, any employees who worked a Sunday should still be paid at time and a half.
Not sure what to suggest - perhaps that the company looks back the timesheets and pays employees who worked any Sundays a top up? Or simply document what was agreed verbally? No employees have challenged it, they understand that it would seem mad to get paid overtime rates when working far less than their normal hours.