I had a few Pre-Orders recent were they used Royal Mail and expected Delivery changed to the Following Monday Week after original release date and would not arrive at earliest the Thur/Fri before there expected delivery date or would not arrive till the following Mon/Tue/Wed/Thur/Fri
I contacted Them to complain about late delivery and asked them to tell warehouse staff to remember Rep Of Ireland they should be using An Post not Royal Mail
All my Amazon Pre-Orders in last 3 Weeks have been An Post except 1 order they used Royal Mail and An Post packages arrived as usual on the Tue (The day after release date)

while Royal Mail package did not arrive till The Friday following week
Go to your account check your order details and see who they used for Delivery it will say Royal Mail when it should have been An Post (1 package via An Post) and not used (1 package via Royal Mail)
You end up wondering if its lost in the post when they use Royal Mail
Note this only applies to
Pre-Orders from Amazon and Amazon in Stock items
Rep Of Ireland delivery should always be package via An Post
If they keep doing this contact them to remind them especially with Temp staff for Christmas been used
Note Third party sellers will always use Royal Mail