The Institute of Criminal Justice Studies (ICJS) at Portsmouth University has an excellent "external programme" of Bachelor and Masters Programmes and has recently launched a Professional Doctorate Programme in criminal justice.
I recently completed an MSc in International Criminal Justice on an external basis. The learning environment and support is excellent. There are also special study schools which enable external and campus students to mix and get to know each other.
You should check out the ICJS programmes on Portsmouth's web-site.