L1949: I did not include these three aircraft as left the fleet last year.
At the moment I think the Jet2 733/738 fleet has 49 aircraft having a total age of 921 years giving an average of 18.8 years (includes 5 new aircraft)
757 fleet has 11 aircraft with a total age of 288 years average 26.18
Total 1209 years, 60 aircraft 20.15 years
If you assume the 10 oldest aircraft will be replaced this will be the 733/738 age down to 12.67, this could be the position in a years time.