FRatSTN
Personally, I think Jet2 will be better off using A330's to dip their toe into the long-haul market if they so desired. It's a known type to them and if they could seek to utilise the same arrangements as they have done in the past with Air Tanker, there's less risk involved whilst they work out if the attempt to diversify is successful or if it's best left served to others. The 787's may have low operating costs being a new generation aircraft, but I expect the acquisition and leasing costs for them to be expensive.