flyglobespan has an average fleet age of 6.1 years, Out of the 16 UK airlines ive included GSM is 3rd.
As a comparison
Palmair has 34 years
Jet 2 has 20.5 years
Loganair has 18.1 years
Air Southwest has 16.4 years
bmi baby has 13.3 years tied with Eastern also at 13.3 years
Monarch has 13.1 years
British Airways has 11.4 years
First Choice/thomsonfly has 10 years
Astraeus has 7.9 years
Virgin Atlantic has 7 years
bmi has 6.3 years
FlyBe has 4.9 years
Easyjet has 3.3 years
Actually the youngest is 2.8 years with Ryanair (though as thats an irish company i havent included it)