Will they flower again next year, TG?
Well they would considering they are technically a perennial, but they tend to be a short lived!
They tend to get a bit woody in later years (assuming they survive) and never seem to flower as well after the first flush so for this reason I replace them every year.
I tend to only sow part of the packet each year so indirectly I get the perennial affect from a packet but better flowers and plants each year by sowing just enough for my needs.
I realise the resulting % germination can drop as the seed gets older, so to cater for this. I sow roughly 20% of the packet in the first year 30% the next and 50% on year three.
This seems to work quite well for me i.e. I get a similar number of plants each year from one packet.