Hello. I wasnt FA on the Concorde but I was Ground staff at LHR on the Concorde Team for many years. The Concorde had two flights a day to JFK the BA001 at 1030 and the BA003 at 1900.
We also had Concorde flights to Barbados during the summer months for many years to cater for the lucky few.
I have travelled on the Concorde several times and the aircraft did turn around and return as the BA 002 and the BA 004 on the same day.
The BA 004 arrived at LHR at about 2225 and was almost the last flight in.
When I travelled out on the BA003 at 1900 we arrived JFK at about 1725 I think, which was really strange as we landed before we had taken off! The flight time if I remember correctly was approx 3hr20mins.
Sorry I cant help you with the life of an FA on Concorde, but I would have thought it was rather like the life of EF CC rather than WW.
Hope this helps.