Thanks Mitre & blueeagle69 - Doh! (this is not going to well)
It must be the one line in the build.prop that needs changing as well, which I can not at the mo' as it causes a bootloop! - Damn and blast.
Unless I need to clear the dalvik cache too as I have only cleared the data from the market app - Also I did read something about it can take market up to 24hrs to catch up.