I dont know about that but normally, a big company such as
Wiggle,
Halfords,
Chain Reaction etc etc would have contracts in place with logistics/couriers who get paid an agreed amount every year to deliver their goods for them. Its not done by a package by package basis like when you walk in to the post office and have them send a parcel for you, They have to have hundreds of items packaged and sent out by the end of the day by. Either the courier they have a contract with will show up in a big van or lorry to collect every 4-12hrs and take goods to their depot for processing (depending on the volume of goods that need to be sent out) or the seller will have their own vehicles to drop the goods that need to be delivered at their couriers depot. Normally it would be the courier that comes out to pick things up.
Its just quicker when youre dealing with high volume or bulk.
On the odd occasion where their contracted courier has failed multiple times to deliver or collect items that need to be returned. customer service will normally book a one off service with an entirely different courier to do a delivery or collection -- This doesnt always happen but some companies will do this as its a one off as it doesnt happen very often.
I say this with 6 years of working for Royal Mail, having done a very short amount of time with DHL and dealing with a lot of customer service departments. Not saying that im 100% keyed in and know how everything works but this is the most logical way and one with the least headache.
I cant tell you if they have to meet a certain target for deliveries and collections every year to keep the contract -- that's something which was beyond my pay grade. I just know that contracts with big companies are worth a lot of money
Thats how logistics companies like Eddie Stobart & such earn their millions. Everything is based on contracts.