geoff wrote:

but as much due to the courier's delivery route as anything else

I offer next day delivery as standard, collected from me at some time
after 3pm. From then on, its out of my hands and in the hands of the
courier

Exactly - some parcels will get there at 8.05am, others at 6pm, and a
few (about 2%) won't make it at all, and will take an extra day. All of
it is entirely beyond the control of the company which shipped it
(choice of courier not withstanding).

--
Grunff