To me the being paid for 15 minute break is completely irrelevant. Unless your some union guy who likes to take umbrage at it.
For example they could pay you like £300 a week including paid break
Or they could pay you £700 a week but not pay for your break.
I know what I’d prefer. 
If the money is good go for it mate. And it’s supermarket work so it will be decent. Also no load interaction which is quite rare for a supermarket.
I’ve never worked for Morrisons but I’ve only heard good things about them.
Which depot you applying to btw?