Interesting. Both of those aircraft were, I think, last operated by a Turkish airline (was it FlyAir?) which left massive outstanding Eurocontrol debts on them, and the lessor (I think it was Sunrock) was not at all keen to place them back in Europe because it would have to clear those debts. Hope Jet2 have taken note of that if indeed those are the aircraft that they are taking. There were also some engine overhaul issues on both machines.
Just to be pedantic, there is no such thing as a 757ER. There are heavy gross weight and low gross weight 757s and 757s (of both weight categories) which are ETOPS and non-ETOPS approved. However, there has never been a formal designation of a 757ER. There is absolutely no guarantee that these two aircraft would be ETOPS-equipped or capable, even if they have been ETOPS in the past, since the aircraft needs to be maintained to ETOPS levels if it is to retain its ETOPS capability.