phones stolen in UK are usually sold off-shore b/c they get IMEI barred from all UK networks
if IMEI numbers could easily be changed they would do it instead of exporting them to countries where devices are cheaper, what do not IMEI ban devices.
IMEI banning seems to spreading world wide now with even India banning all chinese fake phones with spoof IMEI's off there networks.
So in short i think people are wasting there time with this subject b/c even criminals can not be bothered with it.