You can move them in autumn, but bear in mind they have quite a long tap root as well as fibrous ones, so try to extract that intact, which means digging down a fair way to make sure you don't break it. You can divide them, but it's not an easy job to do - whenever I've tried it, they died, so I don't do it any more unless I can see two separate taproots.

Thanks Bamboo. Will try to move once just in case they do not make it. Will it be the case of the more established they are the deeper the tap root?

Yes.

I scoured the internet earlier this summer trying to find out if they could be divided but it seems that almost always the clump cannot be split as only one piece survives.
I'm certain that I've had instances where you dig one up and bits break off with roots attached, but never with the colours you want to make more of.
I can't think of any times I've moved them and had them not survive the process though.
The best the internet could come up with for propagation was seed or purchase of named plants.

Have as a back up option purchased some 'lemon sorbet' seeds which I will sow next June. I have loads of purple ones which seems the more dominant colour. I guess you won't know until you try...Must remember the tap root though...

The best way to keep them going is by seed. They will eventually produce lots of seed pods that can be harvested and sown where you want them to come up next year.