Thanks all. So I got my redemption letter today (Tues 20th Sept). I checked back on my phone calls, and the request was made on Wednesday 14th September in the morning. The letter I received today was DATED 14th Sept (same day as my request) and posted 16th September, and arrived at my house on 20th Sept.
As per what Brendan understood, there was indeed a daily interest accrual figure to "add on from the date of this letter" - approx. €5.50 a day on a €150k outstanding tracker.
It's not that I am worried about the interest - and as others, incl. T Mc Gibney have alluded to, in hindsight, I could have made a lump sum that day for the approx. amount outstanding, and just internet banked the balance later. Had I done that, I could have reduced the daily 5.50 interest to practically zero - but I had rang them, and they said wait for the final figure in the post. Again, they had suggested the figure would remain static for 20 days, but it wasn't! (the letter stated the "quote" was valid for 20 days") I guess that was my mistake, allowing the majority of the balance to remain accruing interest while I waited.
Some things cleared up - PTSB have the capability to generate the outstanding balance immediately (14th Sept call, 14th Sept. letter) - they don't need staff to go off checking it for correctness. But it takes them 2 days to send in the post on Friday 16th - €11 extra cost to me from that delay. Arriving Tuesday 20th Sept, means I have incurred another €5.50 for Sat, Sun and Mon, being a grand total of €26.50 in interest.
I went to my bank branch and paid them the outstanding figure + 2 days interest. Will see how much they push for the other €15. They are culpable for a couple of days for slow posting

Perhaps they will just debit it as part of my last repayment before they clear it.
Thanks all.