We have flown from Leeds and Manchester, using Easyjet,Jet2 and Ryanair, and to be honest we've been happy with all of them. Ryanair from Leeds tends to be cheapest (and easiest) for us , but simply compare them last minute before you book. This year we're going out from Leeds (Ryanair) and coming back into Manchester (Easyjet) purely because it worked out cheapest (even including extra taxi costs from Manchester) and gave us a lot more flexibility on dates.
I would suggest you check the accommodation availability first, then choose and book the flights ( - because the prices can rocket in just a few hours), then book the accommodation.
But it really depends on your priorities. This year we needed very specific dates so we booked the flights without even looking at accommodation because we felt that as long as we could get there, we didn't care if we had to sleep on the beach, just as long as we were in Arillas.....
Good luck.