Not sure where it came from but you can see it here under S - https://en.wiktionary.org/wiki/Appendix:Glossary_of_British_military_slang_and_expressions#S

As for other words, I don’t think we do quite so many as the Aussies but there are words like aggro, cheapo, wino, preggo used in every day speech.

Seppo is pretty common in the UK too, particularly in families with people in the forces.

On the concept of blender, I’ve been recently trying to get into Seamly2D/Valentina for pattern drafting - I’d love to see some kind of simple integration format between the two so that the FreeSewing patterns can be easily loaded into Seamly2D instead so the measurement files can be used from there and the pattern tweaked.