From my experience almost all of them pick network a320s regardless due to higher frequencies.
Virgin seems to be more contractors and newer employees, business cabins tend to go empty or are used when flights are completely full, in some cases people can use their own money for cheap upgrades if they are with a smaller company which doesn't restrict it.
No J catering on charter flights, but presumably have it on regular RPT flights to KTA/PHE/BME/ZNE.
Charter flights tend to have snacks or light catering in Y as well.
