Maybe not johnney... Northern Ireland holiday time is in July (2nd and 3rd Week normally) therefore prices from BFS tend to be high.
English holidays tend to be August so you can get good deals as scodaman did hopping over to England first of all. Vice versa in August now some good flight pricing from NI at moment
Agree Jet2 provide great service, using them to PMI in a weeks time and looking forward to great service and flight.........apart from the current hassle with passport control in PMI, but that's outside Jet2 control