Working in our own time at work

Marvel1

I used to work for a supermarket, people who had the shift 1pm to 10pm - time stores closed and 1pm to 4pm on Sundays.

They weren't leaving til 15 mins after, they (management) then changed the shift pattern to 1:15pm to 10:15pm and 1:15pm to 4:15pm.

WibblyGirly

In my experience, this is common in retail that once the shop shuts you stop being paid but still have to stay 10/15 mins later to tidy and cash up.
In one job I was also expected to start 15 mins early for free! The manager there also tried to guilt trip me into working through my breaks since she worked hers but I never did, I'd just go out for my break instead. I also made sure not to turn up early so they couldn't try make me start even earlier!
That was the worst place for free working.

My most recent retail role had us start 15mins before opening but we got a morning break to compensate and an afternoon break to compensate for staying 15mins after but that place was super easy to cash up and get out within 5 mins so the odd time a customer kept us back didn't bother me as I probably had more money for no work due to the quick closing.

getmore4less

YOu are nor wqorking your own time you are working.

Companies can use different rates of pay for different working hours

£0 is a legal wage as long as the totals comply with minimum wage rules.

As this is compulsory overtime you should address the holiday accrual for this time when you address the rate of pay.