So, looking for a solution I thought I'd explore ant's regexs - the statement below works by matching on the version xml tags and groups them along with existing version info before substituting in the ant version properties used as part of the wider build process in the management pack project file
<replaceregexp file="${SCOM.dir}/Pauls.mpproj"
byline="true"
match="(<Version>)([0-9]*\.[0-9]*\.[0-9]*\.[0-9]*)(<\/Version>)"
replace="\1${VersionMajorNo}\.${VersionMinorNo}\.${VersionPatchNo}\.${VersionBuildNo}\3"/>
So
becomes1.0.0.5
11.2.0.278