Yes, and the DPA applies to him/her as an individual. Because individuals can and do contravene the act.A self employed consultant works for a group, company or organisation - he is employed by himself!
Contrast this with a person employed to handle data by a company - they cannot contravene the act as an individual, it is the organisation that employs them that would get into trouble.
The ICO is quite clear. The DPA applies to "any" legal persons.