it depends on which ones I find. The later flowering ones do better for me when I take cuttings before they flower so mid july/august. So they are semi ripe. starting to go woody but still soft at the tip. I also sometimes layer them, peg a bit down cover a joint with soil and leave it to root.
this is the advice from the rhs:

https://www.rhs.org.uk/advice/profile?PID=474

Thank you SBG, I'll try some this summer then. Don't think I've got room for layering though I'd like to have a go.