I seem to think royal mail either works, or fails to miserably! Seems to be fine when i'm in the receive parcels but theres been times when they've delivered it next door without leaving a card, and my neighbour forgot to tell me for like a week! There was one instance of the postie delivering my parcel nextdoor without even knocking on my door 'because it didn't look like i was in' even though i was watching him through the window!! And for some reason if you try to arrange a redelivery on the website the nearest date you can have is 3 days away, but if you find the number for the post office the parcels gone back to you can have it re-delivered the next day
And i echo DCM's comments about customs, sometimes it goes through in hours, but other times you just get the feeling your parcels sat in the corner gathering dust!