Hand delivery

Hi, my wife's PIP review is due and needs to be with them by the 29th May 2023, which is actually a Bank Holiday. Her PIP award expires on the 29th June. I want a short extension as I am working away and will not be able to post the review back to them this week (everything is done, I have completed the review on paper, but I dont have the original document with me so that I can post them together). I get back home this weekend, and so have I have tried to ring them, but got cut off yesterday. I'm ringing them today to but I am on hold and have been for 40 minutes. To cap it all they have sent a reminder that they have not received our completed review and that if it is not received by the 29th my wife's PIP will end. The earliest I can post all of the documents is Tuesday 30th May, I can overnight it and get it there the following day which will be the 31st May. Will the review being delivered a couple of days late trigger the award to stop? So far I've tried to ring them twice and not been able to get through. I send a letter notifying them as well. I sent it yesterday and its already been delivered. Will they take any notice or even log it? ***** Does anyone know or have they delivered a review by hand to their office. Is there a drop box or a doorman to take it (bearing in mind nobody will get it till the following day?) *** Thanks in advance , any advice gratefully received.