If you chop them down now then you should get one last flowering this year. If the then heavily mulch them then they might survive the winter. Best to place them in a frost free greenhouse.

I think this is basically a house plant, which although OK outside for the summer, should be brought back indoors for winter.

Thankyou! I thought it might be an annual. I already had the second flowering I think. I'll do as you both suggest.