I sell a lot of things online, and if possible, I like to use paypal to pay my wholesalers. Not just because most of my customers pay me that way either.

I had a delivery of 2 dozen smoking dragon incense cone holders a while ago. They were so badly moulded they were not fit for purpose. I contacted the supplier who was incredibly unhelpful. The best they would do was a credit note for half the stock, but I needed to buy replacement stock elsewhere.

As I had paid with paypal, I opened a dispute and got all my money back. So much easier and less time consuming.

As to royal mail vs couriers, a lot of the cheaper couriers are franchises and are only as good as the local company. If you live in an area where they care, they are fine. I have had a couple where they have delivered to the wrong house, the wrong village etc, and will argue that their description of the house they left it at fits yours completely, even when they are as different as windsor castle and 10 downing street.

The good couriers are more expensive, but I suppose you get what you pay for. I have had very little trouble with royal mail, and would rather send with them than Yodel any day of the week.