The only reason the A319 can operate the flight is because it will be used by airlines like private air, in a premium configuration and with extra fuel tanks.
No the A321 wouldn’t be able to reach New York from the UK especially with full fuel and payload. So it seem unlikely that it would be with noe of these aircraft.
FCA (First Choice) operate the A321 from East Midlands to Florida…
I’ve seen them when I was flying with easyJet and I’ve talked to the guy who’s done this flight:)