Unfortunately, that "help" actually does make it a little bit more complicated, as now you'll need the employer letter (the one that confirms your job, start date, salary, etc.), or a second letter from someone within the company, explaining the last pay date. If there's a discrepancy between the date on the payslip and the date the pay is deposited, it will need to be explained by someone with authority within the company (HR, your boss, etc.).
UKVI probably won't make any assumptions like "Oh, it's a pandemic, and so this last pay date is a bit weird." But in this case, if you can't get another letter to explain the situation, you'll need to explain it yourself. Hopefully, they will understand, and/or confirm your statement with someone at your company. If everybody has been furloughed, there's not much else you can do.
Weekly payslips going from the beginning of September to the end of March will definitely cover six FULL months, so you're all set there. Now you just need bank statements that span the same six FULL months. If you need to go in branch to have anything printed, they don't need to certify it. You only need to get statements that you print yourself at home authenticated by the bank's stamp.