In message , at 12:58:52 on Mon, 8 Jun 2020,
remarked:

In my case it's a 60 minute round trip back to the shop or a 30
minute round trip to the Post Office.

You don't have a suitable inconvenience store closer?
https://www.parcel2go.com/ is a good source for finding one.

Interesting.

The distances are as the gulls fly and it shows Morrisons as my closest
at 0.69 miles which necessitates swimming across the River Ely to
achieve. The walking distance will be about 1.05 miles so in
comparison with the Post Office will be about 40 minutes.

Why are you prevented from driving the 1.05 miles?
--
Roland Perry