This is use in Australia and is short for ”oops, sorry about that”.

"Ope" is in use in Australia? Sandgroper here and I've never heard it before. Is it only in certain cities, or a generational / social group thing? Or do I just need to get away from screens more often?

It’s probably just me. Tend to pick up things I’ve heard once somewhere.

On the other hand, I hadn’t heard sandgroper before and had to search to find out it meant Western Australian. Although, I definitely don’t get out much.

Sandgroper is just a shibboleth for Perth & WA people, I think, but it might also be generational. I'm old enough that Fat Cat & Humphrey B Bear mean something to me and are a shared experience, but probably not for people younger than me.

Helpful off-topic instructional video: https://www.youtube.com/watch?v=QWv3L6J1YVE

But saying sorry as a pre-emptive "oops didn't mean to step in front of you, mate" (when the other person had clearly walked into you), that has existed in Perth as long as I can remember.

How about Humphrey B. Flaubert (or Humphrey B. Flow Bear, if you prefer)?