Well I'd just wait until the fruit is red, then pick it. Cut it open, take out the seeds, wash and let dry. Probably best to wait until next spring to sow them.

Next year you could also try to X your plants yourself.
If they flower at the same time just transfer the pollen with a cotton-tip. If they don't, store the pollen on the tip in a zip-lock bag in the fridge.

Thanks Moksha

I did pick some today. They were starting to split. These will probably be all light pink as only pink plants were flowering when they set.
I have another batch set that I am waiting for because I only had single flowers of different colours flowering at the same time. Plus there was a Lobivia flowering as well that has also set seed. So I should get some X for next spring sowing.
What would be the best way to store them? Envelope or air tight contaner?

Thanks again for your help
Rose

I don't think seeds are fussy, an envelope would be fine.

Thanks for the tip about Hyne's(Heyne's?) Nursery, I presume you mean the one at Beulah Park. I went and had a look. It's excellent for succulents, got the best range I've seen in SA, not really that much in the way of cacti though. I think if I want a Stenocereus, I'll have to get hold of some seed.

I like the old established succulents in the front yard of the house across the road too. ; )