Hope it went well.

Not a native, and on many invasive lists, Elaeagnus angustifolia. Here is a link that might be useful: Elaeagnus angustifolia

Thanks everyone. I couldn't ask the owners 'cos my father was renting the house - and in several years of renting it over the summer they've never had any contact with the owners personally, just an agent. And it's really not worth all the trouble of working that far backwards on the off chance they know what they are. They're pretty obviously "volunteers", not something that was intentionally planted. As for the specific guesses, no, it's definitely not money plant - I know that well - nor the Quincula from the pics I saw when I googled that. Thanks, Carol, yes, that's it, but it's in a back yard, and I'm not really comfortable being more specific about the location in so public a venue since it's not my house. And unfortunately I didn't see it anywhere else in a more public location. Oh well, it's not the end of the world. Some day I'll find out - it was unusual enough that I'll definitely remember it. I figured there was a slight chance someone might have noticed it themselves (somewhere else) since it seemed so unusual.

Certainly a Banksia - but what you actually seem to have is not a seed at all, but a dead flower-head, cut before the seeds have formed. I am sure a bit of searching on the internet would find you a picture of a seedhead, for comparison. Trish