I think those Jet2 flights are basically scheduled charters, mostly sold through Jet2 holidays. I think the aircraft even stay in New York for the duration of the stay.
LHR certainly had a 5th daily summer rotation for a number of years, think it used to be a W pattern from DUB. I guess that slot is being used for BHD or SNN services these days. ORK seems to be in a difficult place at the moment for EI. On one had there are opportunities for additional flights and routes here and there, such as a 5th daily LHR, increasing frequency to Paris, possibly taking over some BHX and MAN routations by mainline, or frequency increases at Regional. The problem is that both the Regional and Mainline fleets are pretty stretched at the moment and there is no large-scale order of new aircraft. the VS contract takes care of the new mainline arrivals and the new Regional fleet is backfilling mainline out of DUB and replacing older units. It would seem a mixture of commercial and strategic reasons are conspiring agains expansion at ORK for the present time.