Generally speaking one removes the old leaves from them in February. You can certainly remove the flower stems to stop self seeding all over the place, but the plant needs its leaves to build up strength for next season.

Thanks for the info Owdboggy, would it be ok to cut some of the real tatty leaves of but leave most of them on :o))

Yes, on the basis of one old leaf for signs of one new leaf. You could chop them all off, but that would weaken the plant for next year.

Really, I would like to reduce it in size, can one split these plants into two?

Oh! Owdboggy. I've already asked you that question once LOL, September you told me, silly old brain :o))

Again the answer is yes, but the expert opinion is that it is best done in early Autumn when these plants make new roots. Avoid letting the roots dry out, they hate that. I tend to dunk them in water until I am ready to re-pot.

Thanks Again Owdboggy :o))