Lav, the aircraft have been phased out due to noise requirements which came into force earlier this year, which meant that ICAO Chapter 2 aircraft, had to be withdrawn or hushkitted by 1st April I think it was. A hush kit was made for the aircraft and testing started, also a RR Tay? conversion was considered. Both these options were probably too expensive in relation to the remaining life and value of the airframes. They are still used in the 'undeveloped' world in their unmodified state where noise regs are not any where near as extensive. They can also be operated into Europe as VIP/Emergency/relief flights or to/from maintenance.