Default [Q] Help with build.prop editing please

How can I edit my build.prop to make my xperia SP appear as a generic UK version so it will update to 4.3?

I've tried editing the following from

ro.semc.version.cust=1272-7168 (EE)
ro.semc.version.fs EE-LTE


ro.semc.version.cust=1270-7689 (generic UK)
ro.semc.version.fs GLOBAL-LTE

But it still says no updates available, are there other settings I need to change or have I used the wrong .cut or .fs number?

Any help appreciated, id rather have generic UK than an australian version.