We get that a lot in Essex too. Yesterday evening minutes after we got home from work, UPS failed to deliver a rather large box (new Computer) to our first floor flat. But managed to put the attempted delivery card through letter box.   It is a small flat. There is no way we would not have heard, if he had bothered to knock.

I have had bad experiences with the private delivers and really great ones. One guy rather than take back item back to Ipswich depot next morning (he lived in same town as us in Essex) left a note with his number and if we reached him before 9pm he would bring it out to us that evening.