Work won't pay correct pay on time.

[Toastednose]

Underpaid by about 60 quid last month. New company, TUPEd over so old contract still stands.

They've now said they cant/won't rectify the amount missing until next month.

I only work 2 shifts a week, they've effectively withheld an entire shifts pay for a month for no reason other than a user error on their half.

YANBU to expect the missing pay be paid ASAP instead of next month

YABU they're able to hold that pay back until next payroll

They need to do a bacs transfer. In my experience they usually do an advance and then take it back the following month.

Depending on your salary, this may have taken you below minimum wage which would mean they've broken the law and need to rectify it ASAP.