Their drivers are under so much pressure to finish their delivery rounds that, if it seems that it will take them more than a minute to find the address they have to deliver to, they just write a delivery attempt card and leave.
They don't care if you had to take days off work or that you are expecting time-sensitive documents from the Home Office.
When you talk to the manager supervisor, they lie to cover their mistakes.
This is a company with extremely low quality of service. If you can, AVOID THEM LIKE THE PLAGUE! If you can't (unfortunately their services are one of the cheapest, reason why they had their contract with the Home Office renewed), make sure you contact them via Facebook or their chat system so you can hold proof of what they say to you.