Next January we have a wedding to attend in New York. We'd like to have a holiday in the Caribbean, before or after. I'll have a 2-4-1 but believe I can only use BA flights, so I'm looking for the best (with cost a factor) way of doing the journey, be it a 2-4-1 to JFK, then paid onward flights or MFU? All my previous reward flights have been on BA going from point to point, rather then deviating.