Thank you for your answer. This is exactly what I needed to know and understand.
His payslips don't include a From-To date range on them. They just have a Pay Date and Pay Type, which states:
Pay Date 27-Feb-2019
Pay Type 2-Weekly
His bank statements run from 3rd of month - 2nd of next month.
So I will need Feb, March, April, May, June, July, August .... and then his last payslip will go in 2 days after the August statement (3rd of Aug - 2nd of Sept). So he should be able to go into the bank branch and have them print out an amended statement for 3 Sept - 4 Sept, correct? That shouldn't be a problem, right? (as long as it is stamped or has a letter with the printed 2 day statement)
Also ... while I have your expert eyes reading this ... may I ask another question?

He gets paid every 2 weeks - same amount. With one exception which was in April - he only got one paycheck which covered a 3 week period. This is b/c the employer's pay dates were not in sync with HRMC ( I think this is how they explained it ). So to get back in sync and be on the right schedule for the tax year, they had to do a 3 week pay period as a one off. So that check of course is more than his normal ones but it still all balances out in the wash (so to say). This shouldn't be a problem, right? And should the employer briefly try to explain this in the employment letter?