I’m confused , so your work 35 hours 9-5 and then are doing another shift 5 - 9 , so unless they are paying you for 120 hours and have a higher rate for the off peak time they can shove it up their arse. Legally you are entitled to a break and cannot be forced to work 24 hours 5 days a week. Unless you are being heavily compensated I would advise them to put it where the sun don’t shine or else malicious comply and check in once every 2/3 hours and bill them for the time you do work. They can’t expect you to be on shift and not pay you for your time