I was in a similar situation when I thought UPS weren't going to delivery my application within the 45 days (luckily they delivered it on the deadline day in the end). I phoned the office and explained the situation. The man I spoke to said I should write them an email explaining the situation and attach my evidence that my package had been delayed. I had all the tracking information which showed the delays that had been incurred. He said there were no guarantees that my appeal would be accepted and my deadline extended, but the impression I got was if I could prove it was late because of the courier they would be lenient.