Your mention of eBay is a valid point - our postman has remarked on the fact that most of his deliveries in our street are from eBay vendors.
My personal post has a very high percentage from Amazon, something that didn’t happen a few years ago.
Interesting the way an electronic medium has promoted the use of what was perceived by many as a dying business.
Just enter one address…once you’ve got the account set up you can add all the others.
Well, the London postcode districts are very handy for indicting your rough location in all sorts of entirely non-postal contexts. 
You’re not getting me here. After entering your UK address, it asks if you’ve lived at that address for less than six years. I truthfully answered no, and it took me to a new screen where it asked for my previous address. I truthfully entered my former Irish address, and it said “Invalid postcode.” End of application.
Why not just use RD1 3DW?
(That’s the Postcode of the Red Dwarf, in case anyone was wondering…) 