Hi Duncan,

I guess this may be what you want to do:

    \setuphead[part][placehead=yes]
    \setuphead[section][sectionsegments=section]
    \setuphead[subsection][sectionsegments=section:subsection]
    \starttext
    \part{Part}
    \chapter{Chapter}
    \section{Section}
    \subsection{Subsection}
    \stoptext

I hope it helps,

Pablo
--
http://www.ousia.tk