Coopers carriers or hermes here for the worst service on the planet. With coopers carriers, i think it was in the terms amd conditons that every parcel had to be left standing in water for at least 3 days, lost in the back of the warehouse for another 5 days, especially if they were plants, then kicked from one end of the warehouse to the other when eventually found again before throwing it into the van, then finally when the parcel reached its destination, it was thrown out of the van and onto the ground as hard as they could, thus ensuring that your parcel was well and truly guaranteed to be smashed to pieces. In the end i always stipulated that coopers carriers were not to be used to deliver anything that i bought and to this day, i will complain if ever anything is delivered by them. Hermes are not much better.
On the other hand, Royal mail here are great. I know all the drivers, the parcels are undamaged and nothing is ever lost or damaged, and i love DPD.