Found a good business class fare from Europe to the States (849 euro). Economy ~325 and Premium Economy ~465. I've seen in the past that British offers cash upgrades online from Econ -> Business for their European flights and that they're often much cheaper than buying a business class ticket initially. Is this the same for transatlantic flights? Would I be better off buying an Econ or Premium Econ ticket and hoping for a good upgrade deal online or just buying the Business ticket? Thanks in advance for the advice.