Now that a YES has been voted through my concern is the ability to get the back pay right. Once you factor in back pay(including any spine point increases), OJTI pay(both activation and hourly payment, with a spine point increase in april), Pension and NI it becomes a very complicated affair. How is anyone supposed to be able to check that it is all correct when it finally gets paid.
Answers on a postcard.
I'm sure the guys in payroll often come round to check that you're doing your job right! Leave it to the people who are paid to do it
Best option when you get your July payslip is to make sure the gross payments are right. i.e. check your gross pay and allowances against the published pay scales. Any errors here should be highlighted to HR.
If the gross payments are right then the guys in payroll will take care of the rest. 4,000 amateurish PAYE calculations will just make their day I bet!