My experience with Hermes is that they take at least a week to deliver anything. It finally arrives and doesn't seem to be abused, though, which I guess is fine if you're not in a rush and want to save a few quid. Literally, a few quid.
From what I understand about Paisley, which I have no experience of, is that they are a middle man rather than an actual courier, so thats why TNT etc will pick up and delivery your parcels. That also kind of explains why they miss pick ups, they're also relying on numbers other companies to do their bit.