[acqq]

So would a Briton say "I used to work at Goldmans" if the company is called Goldman Sachs?

[scrumper]

Yes, exactly. Same with Lehmans, Merrills, etc. Mostly companies named after people.

[pests]

In southeast Michigan its also standard for people to append an `s` to the end of most stores.

Kroger -> Krogers Meijer -> Meijers

etc. I never noticed it until I went on a linguistics bender on Wikipedia where it was noted.