Can we not just get rid of the traffic instead?

My mouth 😃

Probably worth potting on once into a slightly bigger pot, the extra food should encourage some new leaf growth, but in my experience they flower and then senesce.

Don't split them, the added stress will encourage flowering.

Might be a factor of living well north of the equator and shorter days (Scotland), but overwintering is not something that's possible for us. It's an annual plant: grow, flower, seed, die.

Better to sow more seed or buy another supermarket pot and pot in on straight away so it never gets a chance to be stressed by lack of nutrients.

Tried to grow them in our greenhouse and failed. (Scotland)

No idea where to buy them, just pointing they're quite hard to grow here.