[How?] Replace default phrase with mod/plugin

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Title says it all really...I'm creating a mod but want to replace a default phrase with my own, how can I do this using the mods xml file rather then user having to do it manually from admincp phrase manager?

I tried adding the phrase to my mod:

<phrases>
<phrasetype name="GLOBAL" fieldname="global">
			<phrase name="Original phrase" date="xxxxxxxxx" username="xxxxxx" version="x.x"><![CDATA[My replacement]]></phrase>
</phrases>
</phrasetype>

and ticked the overwrite box when installing mod xml but to no avail.

Also what would the uninstall code be if user was to uninstall the mod so phrase would go back to default?