I made my first purchase about 1998. Ihad a three quarter zip up jacket and the zip went and I soon discovered that it was not a standard UK size. I trailed around locally and even went to the haberdashery department in the Oxford Street branch of John Lewis, but to no avail.
I really liked the coat and didn't want to ditch it, so I decided to try the internet. My first search located a zip retailer somewhere in the USA with the right length zip and the right colour. It was only a couple of £s, even with postage, so I decided to risk it. 10 days later my zip arrived, it was put in and I wore the coat for some years more.
Fast forward 20 years. The zip on a outdoor activity anorak went. This time I could get the length in the UK, but not the colour, so I went online. I swear that the American company that came up with the right colour zip was the same one I bought from 20 years ago!
To think that London, or anywhere else for that matter, does not belong to any one demographic