Final solution has turned out to be
- Mercurial (http://mercurial.selenic.com/)
- EasyMercurial GUI* - very simple and tidy interface (http://easyhg.org/)
- HgLab self-hosted server and repository manager. Was a little fiddly to set up but not too bad (http://hglabhq.com/)
*EasyMercurial has some limitations, however, it was by far the easiest to understand and get to grips with. May move to a more sophisticated GUI later.