Wage deductions in final weeks. Should I hold final paperwork until settled?

...Ghost...

Hi, please stick with me while I flesh this out a bit. I'm serving my notice period with current employer and due to start new job next week. I gave 4 weeks notice out of courtesy where I really only needed to give a week having recently completed probation. This week is my last week.

I get paid weekly and had offered to work weekends if they wanted me to during my notice period to help them work through some backlog. 2 weeks ago, they added a Saturday to my schedule and I got the job done. Last week, I noticed it was not on my payslip and when I queried it, the accounts lady said it would be paid the next week. keep that in mind.

Last Tuesday, I was burning up and tested positive for C19 when I got home. This meant I was unable to complete scheduled work on the Wednesday or Thursday. Friday was a scheduled paperwork day, so I was able to do that in isolation. This week I had asked for annual leave for Monday, Tuesday and Wednesday. At the time of asking, I hadn't considered Paddies Day would be there and wasn't aware of the Bank Holiday this Friday which I had expected to be my last day at work.

So I got my payslip today and I was only paid for 1 day last week. This leaves me in a bit of a financial pickle and I will have to resort to using the credit card for basics. The Saturday I was owed still had not been paid. I contacted accounts and the accounts lady apologised when I explained I had worked the Monday and Tuesday.....that I was unable to work the Wednesday and Thursday, but had Friday as a paperwork day. She told me that she had put through the Saturday pay, but had been over-ridden on that by someone more senior. She said she would put it through for next week, along with the 2 missing days and I asked for this in writing, which I promptly received.

I have also sent them an email to point out that I had given my 4 weeks notice and there was no request to bring that forward, or delay it. As such, I am still employed by them until the end of the week and should be paid as such, including the missing 2 days from last week and the remaining holiday pay. With there being 3 questionable current and pending deductions which I believe are or will be seen as illegal under the Payment of Wages Act 1991; namely:

a) Missing Saturday pay for 2 weeks in a row.

b) Missing 2 days from last week.

c) Potential non payment for the upcoming public holidays this Thursday & Friday.

I have and fully intent to complete some paperwork for the company which will take me a couple of hours, including the posting receipts and invoices back to HQ for their accounts. I am however wondering if I should await full and final settlement of my wages before submitting the paperwork, which is part of the work I completed during the days they have not paid me. I don't like the idea personally, but if they're not going to pay me for my work, I perhaps shouldn't submit the paperwork which finalises the work I had done for them. They don't pay sick-pay and I caught Covid because of the high risk environments I am exposed to most work days (which is partly why I am leaving the company).

I'm really annoyed at how certain people in the company have behaved in recent weeks since I handed in my notice. You would think I had a wee in their cornflakes. This seems to have had a direct impact on my wages in the last 2 weeks and likely next week too. Anyone got advice in how to deal with this, or have I so far taken the right steps to a clean break? This is partly just a rant, but I would be interested in any constructive viewpoints on this and what I could/should do if they continue to act the maggot.