OK, whilst messing about with my Z320i i ran across a few codes which allowed me to along with other things change my IMEI number,

*#123580#

which will bring you to the test screen,

after which you can put commands in from 00 - 99, all 2 digit numbers

comand 90 brings up IMEI reset

put in a 14 digit number and hit your centre button till save, restart phone with command 05 and your new IMEI will be on