A couple of comments:
It is the responsibility of the able bodied person sitting by the overwing exit to open it in the event an evacuation is required
During my past few flights as SLF the passengers sitting next to the overwing exits seem:
a) not to be able-bodied (old, infirm, young);
b) seemed to appreciate the extra leg room afforded by pre-booking the seat; and
c) were not briefed by cabin crew before the flight (verbally and/or to ensure safety card had been read and understood.
Please note these comments DO NOT relate to Jet2 flights.