Q. Can you help me find and reference Driscoll's reflective cycle?

You can find Driscoll's discussion of the development of his reflective cycle in Driscoll's Practising clinical supervision on page 43.

Your Harvard style in-text citation would be Driscoll (2007, p.43) or (Driscoll, 2007, p.43).

A full Harvard reference for your reference list would look like this:

Driscoll, J. (2007) Practising clinical supervision: a reflective approach for healthcare professionals. 2nd edn. Edinburgh: Bailliere Tindall Elsevier.