Theyre tender herbaceous perennials, so they may survive in warmer parts of the country but usually the frost kills them. If yours have survived, hard to say why they're not producing flowers without knowing growing conditions, so more info please. Have you fed them, are they still in pots, bigger pots than last year's?

with it being such a weird weather year that may be the reason. they need a bit of warmth and sunshine so that flowers can form.

Yes you can! They multiply well here in southern England, tho not as large as the european plants I have seen. Those plants are pretty, mine are much leafier, if that's a word.lol.